define "Initial Population":
  AgeInYearsAt(date from 
    end of "Measurement Period"
  ) in Interval[18, 85]
    and exists "Essential Hypertension Diagnosis"
    and exists AdultOutpatientEncounters."Qualifying Encounters"

define "Denominator":
  "Initial Population"

define "Denominator Exclusions":
  Hospice."Has Hospice Services"
    or exists ( "Pregnancy or Renal Diagnosis" )
    or exists ( "End Stage Renal Disease Procedures" )
    or exists ( "End Stage Renal Disease Encounter" )
    or AIFrailLTCF."Is Age 66 to 80 with Advanced Illness and Frailty or Is Age 81 or Older with Frailty"
    or AIFrailLTCF."Is Age 66 or Older Living Long Term in a Nursing Home"
    or PalliativeCare."Has Palliative Care in the Measurement Period"

define "Numerator":
  "Has Systolic Blood Pressure Less Than 140"
    and "Has Diastolic Blood Pressure Less Than 90"

define "Qualifying Encounters":
  ( ( [Encounter: "Office Visit"]
    union [Encounter: "Annual Wellness Visit"]
    union [Encounter: "Preventive Care Services Established Office Visit, 18 and Up"]
    union [Encounter: "Preventive Care Services Initial Office Visit, 18 and Up"]
    union [Encounter: "Home Healthcare Services"]
    union [Encounter: "Virtual Encounter"]
    union [Encounter: "Telephone Visits"] ).isEncounterPerformed() ) ValidEncounter
    where ValidEncounter.period.toInterval() during day of "Measurement Period"

define "Has Hospice Services":
  exists ((([Encounter: "Encounter Inpatient"]).isEncounterPerformed()) InpatientEncounter
      where (InpatientEncounter.hospitalization.dischargeDisposition ~ "Discharge to home for hospice care (procedure)"
          or InpatientEncounter.hospitalization.dischargeDisposition ~ "Discharge to healthcare facility for hospice care (procedure)"
      )
        and InpatientEncounter.period.toInterval() ends during day of "Measurement Period"
  )
    or exists ((([Encounter: "Hospice Encounter"]).isEncounterPerformed()) HospiceEncounter
        where HospiceEncounter.period.toInterval() overlaps day of "Measurement Period"
    )
    or exists ((([Observation: "Hospice care [Minimum Data Set]"]).isAssessmentPerformed()) HospiceAssessment
        where HospiceAssessment.value ~ "Yes (qualifier value)"
          and HospiceAssessment.effective.toInterval() overlaps day of "Measurement Period"
    )
    or exists ((([ServiceRequest: "Hospice Care Ambulatory"]).isInterventionOrder()) HospiceOrder
        where HospiceOrder.authoredOn.toInterval() during day of "Measurement Period"
        // and HospiceOrder.doNotPerform is not true
        // https://oncprojectracking.healthit.gov/support/browse/CQLIT-447
    )
    or exists ((([Procedure: "Hospice Care Ambulatory"]).isInterventionPerformed()) HospicePerformed
        where HospicePerformed.performed.toInterval() overlaps day of "Measurement Period"
    )
    or exists (([Condition: "Hospice Diagnosis"]) HospiceCareDiagnosis
        where HospiceCareDiagnosis.prevalenceInterval() overlaps day of "Measurement Period"
    )

define "Has Criteria Indicating Frailty":
  exists ( (([DeviceRequest: "Frailty Device"]).isDeviceOrder()) FrailtyDeviceOrder
      where FrailtyDeviceOrder.doNotPerform() is not true
      and FrailtyDeviceOrder.authoredOn.toInterval() during day of "Measurement Period"
  )
    or exists ( (([Observation: "Medical equipment used"]).isAssessmentPerformed()) EquipmentUsed
        where EquipmentUsed.value as Concept in "Frailty Device" 
        and EquipmentUsed.effective.toInterval() ends during day of "Measurement Period"
    )
    or exists ( ([Condition: "Frailty Diagnosis"]) FrailtyDiagnosis
        where FrailtyDiagnosis.prevalenceInterval() overlaps day of "Measurement Period"
    )
    or exists ( (([Encounter: "Frailty Encounter"]).isEncounterPerformed()) FrailtyEncounter
        where FrailtyEncounter.period.toInterval() overlaps day of "Measurement Period"
    )
    or exists ( (([Observation: "Frailty Symptom"]).isSymptom()) FrailtySymptom
        where FrailtySymptom.effective.toInterval() overlaps day of "Measurement Period"
    )

define "Has Advanced Illness in Year Before or During Measurement Period":
exists ([Condition: "Advanced Illness"] AdvancedIllnessDiagnosis
where AdvancedIllnessDiagnosis.prevalenceInterval() starts during day of Interval[start of "Measurement Period" - 1 year, end of "Measurement Period"])

define "Has Dementia Medications in Year Before or During Measurement Period":
  exists (( ([MedicationRequest: medication in "Dementia Medications"]).isMedicationActive()) DementiaMedication
        // https://oncprojectracking.healthit.gov/support/browse/CQLIT-449
      where DementiaMedication.medicationRequestPeriod() overlaps day of Interval[start of "Measurement Period" - 1 year, 
        end of "Measurement Period"]
        // and DementiaMedication.doNotPerform is not true
        // https://oncprojectracking.healthit.gov/support/browse/CQLIT-447
  )

define "Is Age 66 to 80 with Advanced Illness and Frailty or Is Age 81 or Older with Frailty":
  ( AgeInYearsAt(date from end of "Measurement Period")in Interval[66, 80]
      and "Has Criteria Indicating Frailty"
      and ( "Has Advanced Illness in Year Before or During Measurement Period"
          or "Has Dementia Medications in Year Before or During Measurement Period"
      )
  )
    or ( AgeInYearsAt(date from end of "Measurement Period")>= 81
        and "Has Criteria Indicating Frailty"
    )

define "Is Age 66 or Older Living Long Term in a Nursing Home":
  AgeInYearsAt(date from 
     end of "Measurement Period"
  )>= 66
    and ( ( Last( (([Observation: "Housing status"]).isAssessmentPerformed()) HousingStatus    
          where HousingStatus.effective.toInterval() ends on or before 
          day of end of "Measurement Period"
          sort by 
          end of effective.toInterval() asc
      )) LastHousingStatus
        where LastHousingStatus.value ~ "Lives in a nursing home (finding)"
    ) is not null

define "Has Palliative Care in the Measurement Period":
  exists ((([Observation: "Functional Assessment of Chronic Illness Therapy - Palliative Care Questionnaire (FACIT-Pal)"]).isAssessmentPerformed()) PalliativeAssessment
      where PalliativeAssessment.effective.toInterval() overlaps day of "Measurement Period"
  )
    or exists ([Condition: "Palliative Care Diagnosis"] PalliativeDiagnosis
        where PalliativeDiagnosis.prevalenceInterval() overlaps day of "Measurement Period"
    )
    or exists ((([Encounter: "Palliative Care Encounter"]).isEncounterPerformed()) PalliativeEncounter
        where PalliativeEncounter.period.toInterval() overlaps day of "Measurement Period"
    )
    or exists ((([Procedure: "Palliative Care Intervention"]).isInterventionPerformed()) PalliativeIntervention
        where PalliativeIntervention.performed.toInterval() overlaps day of "Measurement Period"
    )

define "SDE Sex":
  case
    when Patient.gender = 'male' then "M"
    when Patient.gender = 'female' then "F"
    else null
  end

define "SDE Payer":
  [Coverage: type in "Payer Type"] Payer
    return {
      code: Payer.type,
      period: Payer.period
    }

define "SDE Ethnicity":
  Patient.ethnicity E
    return Tuple {
      codes: { E.ombCategory } union E.detailed,
      display: E.text
    }

define "SDE Race":
  Patient.race R
    return Tuple {
      codes: R.ombCategory union R.detailed,
      display: R.text
    }

define "SDE Sex":
  SDE."SDE Sex"

define "Qualifying Systolic Blood Pressure Reading":
  ( ( ["observation-bp"] ).isObservationBP ( ) ) BloodPressure
    where ( not ( ( BloodPressure.encounter.getEncounter ( ) ).class.code in { 'EMER', 'IMP', 'ACUTE', 'NONAC', 'PRENC', 'SS' } ) )
      and BloodPressure.effective.latest ( ) during day of "Measurement Period"

define "Qualifying Diastolic Blood Pressure Reading":
  ( ( ["observation-bp"] ).isObservationBP ( ) ) BloodPressure
    where ( not ( ( BloodPressure.encounter.getEncounter ( ) ).class.code in { 'EMER', 'IMP', 'ACUTE', 'NONAC', 'PRENC', 'SS' } ) )
      and BloodPressure.effective.latest ( ) during day of "Measurement Period"

define "Blood Pressure Days":
  ( "Qualifying Diastolic Blood Pressure Reading" DBPExam
      return date from DBPExam.effective.latest ( )
  )
    intersect ( "Qualifying Systolic Blood Pressure Reading" SBPExam
        return date from SBPExam.effective.latest ( )
    )

define "Most Recent Blood Pressure Day":
  Last("Blood Pressure Days" BPDays
      sort asc
  )

define "Lowest Systolic Reading on Most Recent Blood Pressure Day":
  First("Qualifying Systolic Blood Pressure Reading" SBPReading
      where SBPReading.effective.latest() same day as "Most Recent Blood Pressure Day"
      return singleton from(SBPReading.component SBPComponent
          where SBPComponent.code ~ "Systolic blood pressure"
          return SBPComponent.value as Quantity
      )
      sort asc
  )

define "Has Systolic Blood Pressure Less Than 140":
  "Lowest Systolic Reading on Most Recent Blood Pressure Day" < 140 'mm[Hg]'

define "Lowest Diastolic Reading on Most Recent Blood Pressure Day":
  First("Qualifying Diastolic Blood Pressure Reading" DBPReading
      where DBPReading.effective.latest() same day as "Most Recent Blood Pressure Day"
      return singleton from(DBPReading.component DBPComponent
          where DBPComponent.code ~ "Diastolic blood pressure"
          return DBPComponent.value as Quantity
      )
      sort asc
  )

define "Has Diastolic Blood Pressure Less Than 90":
  "Lowest Diastolic Reading on Most Recent Blood Pressure Day" < 90 'mm[Hg]'

define "Numerator":
  "Has Systolic Blood Pressure Less Than 140"
    and "Has Diastolic Blood Pressure Less Than 90"

define "Essential Hypertension Diagnosis":
  ( [Condition: "Essential Hypertension"] ) Hypertension
    where Hypertension.prevalenceInterval ( ) overlaps Interval[start of "Measurement Period", start of "Measurement Period" + 6 months )

define "Initial Population":
  AgeInYearsAt(date from 
    end of "Measurement Period"
  ) in Interval[18, 85]
    and exists "Essential Hypertension Diagnosis"
    and exists AdultOutpatientEncounters."Qualifying Encounters"

define "Denominator":
  "Initial Population"

define "SDE Payer":
  SDE."SDE Payer"

define "SDE Ethnicity":
  SDE."SDE Ethnicity"

define "Pregnancy or Renal Diagnosis":
  ( [Condition: "Pregnancy"]
    union [Condition: "End Stage Renal Disease"]
    union [Condition: "Kidney Transplant Recipient"]
    union [Condition: "Chronic Kidney Disease, Stage 5"] ) PregnancyESRDDiagnosis
    where PregnancyESRDDiagnosis.prevalenceInterval ( ) overlaps "Measurement Period"

define "End Stage Renal Disease Procedures":
  ( ( [Procedure: "Kidney Transplant"]
      union [Procedure: "Dialysis Services"]
  ).isProcedurePerformed ( ) ) ESRDProcedure
    where ESRDProcedure.performed.toInterval ( ) ends on or before end of "Measurement Period"

define "End Stage Renal Disease Encounter":
  ( ( [Encounter: "ESRD Monthly Outpatient Services"] ).isEncounterPerformed ( ) ) ESRDEncounter
    where ESRDEncounter.period.toInterval ( ) starts on or before end of "Measurement Period"

define "Denominator Exclusions":
  Hospice."Has Hospice Services"
    or exists ( "Pregnancy or Renal Diagnosis" )
    or exists ( "End Stage Renal Disease Procedures" )
    or exists ( "End Stage Renal Disease Encounter" )
    or AIFrailLTCF."Is Age 66 to 80 with Advanced Illness and Frailty or Is Age 81 or Older with Frailty"
    or AIFrailLTCF."Is Age 66 or Older Living Long Term in a Nursing Home"
    or PalliativeCare."Has Palliative Care in the Measurement Period"

define "SDE Race":
  SDE."SDE Race"

define fluent function getEncounter(reference Reference):
  singleton from ( [Encounter] E
      where E.id = reference.reference.getId ( )
  )

/*
@description: Converts the given [Period](https://hl7.org/fhir/datatypes.html#Period)
value to a CQL DateTime Interval
@comment: If the start value of the given period is unspecified, the starting
boundary of the resulting interval will be open (meaning the start of the interval
is unknown, as opposed to interpreted as the beginning of time).
*/
define function ToInterval(period FHIR.Period):
    if period is null then
        null
    else
        if period."start" is null then
            Interval(period."start".value, period."end".value]
        else
            Interval[period."start".value, period."end".value]

define function ToString(value uri): value.value

/*
@description: Converts the given FHIR [Coding](https://hl7.org/fhir/datatypes.html#Coding) value to a CQL Code.
*/
define function ToCode(coding FHIR.Coding):
    if coding is null then
        null
    else
        System.Code {
          code: coding.code.value,
          system: coding.system.value,
          version: coding.version.value,
          display: coding.display.value
        }

/*
@description: Converts the given FHIR [CodeableConcept](https://hl7.org/fhir/datatypes.html#CodeableConcept) value to a CQL Concept.
*/
define function ToConcept(concept FHIR.CodeableConcept):
    if concept is null then
        null
    else
        System.Concept {
            codes: concept.coding C return ToCode(C),
            display: concept.text.value
        }

/*
@description: Returns the tail of the given uri (i.e. everything after the last slash in the URI).
@comment: This function can be used to determine the logical id of a given resource. It can be used in
a single-server environment to trace references. However, this function does not attempt to resolve
or distinguish the base of the given url, and so cannot be used safely in multi-server environments.
*/
define fluent function getId(uri String):
  Last(Split(uri, '/'))

/*
@description: Returns an interval representing the normalized prevalence period of a given Condition.
@comment: Uses the ToInterval and ToAbatementInterval functions to determine the widest potential interval from
onset to abatement as specified in the given Condition. If the condition is active, or has an abatement date the resulting 
interval will have a closed ending boundary. Otherwise, the resulting interval will have an open ending boundary.
*/
define fluent function prevalenceInterval(condition Condition):
if condition.clinicalStatus ~ "active"
  or condition.clinicalStatus ~ "recurrence"
  or condition.clinicalStatus ~ "relapse" then
  Interval[start of condition.onset.toInterval(), end of condition.abatementInterval()]
else
    (end of condition.abatementInterval()) abatementDate
    return if abatementDate is null then
      Interval[start of condition.onset.toInterval(), abatementDate)
    else
      Interval[start of condition.onset.toInterval(), abatementDate]

/*
@description: Returns an interval representing the normalized abatement of a given Condition.
@comment: If the abatement element of the Condition is represented as a DateTime, the result
is an interval beginning and ending on that DateTime.
If the abatement is represented as a Quantity, the quantity is expected to be a calendar-duration and is interpreted as the age of the patient. The
result is an interval from the date the patient turned that age to immediately before one year later.
If the abatement is represented as a Quantity Interval, the quantities are expected to be calendar-durations and are interpreted as an age range during
which the abatement occurred. The result is an interval from the date the patient turned the starting age of the quantity interval, and ending immediately
before one year later than the date the patient turned the ending age of the quantity interval.
*/
define fluent function abatementInterval(condition Condition):
	if condition.abatement is DateTime then
	  Interval[condition.abatement as DateTime, condition.abatement as DateTime]
	else if condition.abatement is Quantity then
		Interval[Patient.birthDate + (condition.abatement as Quantity),
			Patient.birthDate + (condition.abatement as Quantity) + 1 year)
	else if condition.abatement is Interval<Quantity> then
	  Interval[Patient.birthDate + (condition.abatement.low as Quantity),
		  Patient.birthDate + (condition.abatement.high as Quantity) + 1 year)
	else if condition.abatement is Interval<DateTime> then
	  Interval[condition.abatement.low, condition.abatement.high)
	else null as Interval<DateTime>

/*
@description: Normalizes a value that is a choice of timing-valued types to an equivalent interval
@comment: Normalizes a choice type of DateTime, Quanitty, Interval<DateTime>, or Interval<Quantity> types
to an equivalent interval. This selection of choice types is a superset of the majority of choice types that are used as possible
representations for timing-valued elements in QICore, allowing this function to be used across any resource.
The input can be provided as a DateTime, Quantity, Interval<DateTime> or Interval<Quantity>.
The intent of this function is to provide a clear and concise mechanism to treat single
elements that have multiple possible representations as intervals so that logic doesn't have to account
for the variability. More complex calculations (such as medication request period or dispense period
calculation) need specific guidance and consideration. That guidance may make use of this function, but
the focus of this function is on single element calculations where the semantics are unambiguous.
If the input is a DateTime, the result a DateTime Interval beginning and ending on that DateTime.
If the input is a Quantity, the quantity is expected to be a calendar-duration interpreted as an Age,
and the result is a DateTime Interval beginning on the Date the patient turned that age and ending immediately before one year later.
If the input is a DateTime Interval, the result is the input.
If the input is a Quantity Interval, the quantities are expected to be calendar-durations interpreted as an Age, and the result
is a DateTime Interval beginning on the date the patient turned the age given as the start of the quantity interval, and ending
immediately before one year later than the date the patient turned the age given as the end of the quantity interval.
If the input is a Timing, an error will be thrown indicating that Timing calculations are not implemented. Any other input will reslt in a null DateTime Interval
*/
define fluent function toInterval(choice Choice<DateTime, Quantity, Interval<DateTime>, Interval<Quantity>, Timing>):
  case
	  when choice is DateTime then
    	Interval[choice as DateTime, choice as DateTime]
		when choice is Interval<DateTime> then
  		choice as Interval<DateTime>
		when choice is Quantity then
		  Interval[Patient.birthDate + (choice as Quantity),
			  Patient.birthDate + (choice as Quantity) + 1 year)
		when choice is Interval<Quantity> then
		  Interval[Patient.birthDate + (choice.low as Quantity),
			  Patient.birthDate + (choice.high as Quantity) + 1 year)
		when choice is Timing then
      Message(null, true, 'NOT_IMPLEMENTED', 'Error', 'Calculation of an interval from a Timing value is not supported') as Interval<DateTime>
		else
			null as Interval<DateTime>
	end

/*
@description: Returns true if the given DeviceRequest is a negation (i.e. do not perform this order)
*/
define fluent function doNotPerform(deviceRequest DeviceRequest):
  singleton from (
    deviceRequest.modifierExtension E
      where E.url = 'http://hl7.org/fhir/us/qicore/StructureDefinition/qicore-doNotPerform'
      return E.value as Boolean
  )

//Observation Vital Signs
define fluent function isObservationBP(Obs List<"QICore.observation-bp">):
  Obs O
    where O.status in { 'final', 'amended', 'corrected' }

//Encounter, Performed
//General usage unless required otherwise by measure intent (e.g., follow-up encounters)
define fluent function isEncounterPerformed(Enc List<Encounter>):
  Enc E
    where E.status in {'finished', 'arrived', 'triaged', 'in-progress', 'onleave'}

//This library contains functions that are based on QDM 5.6 to QICore 4.1.1 March 2023 (https://github.com/cqframework/CQL-Formatting-and-Usage-Wiki/wiki/Authoring-Patterns---QICore-v4.1.1). The functions may appear similar to some QICoreCommon functions but different in that they have constraints that are relevant for measures authored by NCQA.

//Assessment, Performed
define fluent function isAssessmentPerformed(Obs List<Observation>):
  Obs O
    where O.status in { 'final', 'amended', 'corrected' }
          and exists ( O.category ObservationCategory
          where ( ObservationCategory ) ~ "survey"
      )

//Intervention, Order: active and completed only    
define fluent function isInterventionOrder(ServiceRequest List<ServiceRequest>):
  ServiceRequest S
    where S.status in { 'active', 'completed' }
      and S.intent = 'order'

//Intervention, Performed
define fluent function isInterventionPerformed(Proc List<Procedure>):
  Proc P
    where P.status ~ 'completed'

//Procedure, Performed
define fluent function isProcedurePerformed(Proc List<Procedure>):
  Proc P
    where P.status ~ 'completed'

//Device, Order - Personal Use Devices: active and completed only
define fluent function isDeviceOrder(DeviceRequest List<DeviceRequest>):
  DeviceRequest D
    where D.status in { 'active', 'completed' }
      and D.intent = 'order'

//Symptom
define fluent function isSymptom(Obs List<Observation>):
  Obs O
    where O.status in { 'preliminary', 'final', 'amended', 'corrected' }

//Medication, Active
define fluent function isMedicationActive(MedicationRequest List<MedicationRequest>):
  MedicationRequest M
    where M.status = 'active'
      and M.intent = 'order'

define fluent function medicationRequestPeriod(Request "MedicationRequest"):
  Request R
    let
      dosage: singleton from R.dosageInstruction,
      doseAndRate: singleton from dosage.doseAndRate,
      timing: dosage.timing,
      frequency: Coalesce(timing.repeat.frequencyMax, timing.repeat.frequency),
      period: Quantity(timing.repeat.period, timing.repeat.periodUnit),
      doseRange: doseAndRate.dose,
      doseQuantity: doseAndRate.dose,
      dose: Coalesce(end of doseRange, doseQuantity),
      dosesPerDay: Coalesce(ToDaily(frequency, period), Count(timing.repeat.timeOfDay), 1.0),
      boundsPeriod: timing.repeat.bounds as Interval<DateTime>,
      daysSupply: (convert R.dispenseRequest.expectedSupplyDuration to days).value,
      quantity: R.dispenseRequest.quantity,
      refills: Coalesce(R.dispenseRequest.numberOfRepeatsAllowed, 0),
      startDate:
        Coalesce(
          date from start of boundsPeriod,
          date from R.authoredOn,
          date from start of R.dispenseRequest.validityPeriod
        ),
      totalDaysSupplied: Coalesce(daysSupply, quantity.value / (dose.value * dosesPerDay)) * (1 + refills)
    return
      if startDate is not null and totalDaysSupplied is not null then
        Interval[startDate, startDate + Quantity(totalDaysSupplied - 1, 'day') ]
      else if startDate is not null and boundsPeriod."high" is not null then
        Interval[startDate, date from end of boundsPeriod]
      else
        null

/**********************************************************************/
/* Functions in this region are copied from opioid-mme-r4             */
/**********************************************************************/

define function Quantity(value Decimal, unit String):
  if value is not null then
    System.Quantity { value: value, unit: unit }
  else
    null

/*
 Goal is to get to number of days
 Two broad approaches to the calculation:
  1) Based on supply and frequency, calculate the number of expected days the medication will cover/has covered
  2) Based on relevant period, determine a covered interval and calculate the length of that interval in days
This topic covers several use cases and illustrates how to calculate Cumulative
Medication Duration for each type of medication resource using the supply and
frequency approach.
*/

/*
  For the first approach, we need to get from frequency to a frequency/day
  So we define ToDaily
*/

/*
  Calculates daily frequency given frequency within a period
*/
define function ToDaily(frequency System.Integer, period System.Quantity):
  case period.unit
    when 'h' then frequency * (24.0 / period.value)
    when 'min' then frequency * (24.0 / period.value) * 60
    when 's' then frequency * (24.0 / period.value) * 60 * 60
    when 'd' then frequency * (24.0 / period.value) / 24
    when 'wk' then frequency * (24.0 / period.value) / (24 * 7)
    when 'mo' then frequency * (24.0 / period.value) / (24 * 30) /* assuming 30 days in month */
    when 'a' then frequency * (24.0 / period.value) / (24 * 365) /* assuming 365 days in year */
    when 'hour' then frequency * (24.0 / period.value)
    when 'minute' then frequency * (24.0 / period.value) * 60
    when 'second' then frequency * (24.0 / period.value) * 60 * 60
    when 'day' then frequency * (24.0 / period.value) / 24
    when 'week' then frequency * (24.0 / period.value) / (24 * 7)
    when 'month' then frequency * (24.0 / period.value) / (24 * 30) /* assuming 30 days in month */
    when 'year' then frequency * (24.0 / period.value) / (24 * 365) /* assuming 365 days in year */
    when 'hours' then frequency * (24.0 / period.value)
    when 'minutes' then frequency * (24.0 / period.value) * 60
    when 'seconds' then frequency * (24.0 / period.value) * 60 * 60
    when 'days' then frequency * (24.0 / period.value) / 24
    when 'weeks' then frequency * (24.0 / period.value) / (24 * 7)
    when 'months' then frequency * (24.0 / period.value) / (24 * 30) /* assuming 30 days in month */
    when 'years' then frequency * (24.0 / period.value) / (24 * 365) /* assuming 365 days in year */
    else Message(null, true, 'CMDLogic.ToDaily.UnknownUnit', ErrorLevel, 'Unknown unit ' & period.unit)
  end