Map Dates to Fiscal Periods

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dates

fiscal-year

leap-year

Map Dates to Fiscal Periods

Not every company closes its books on December 31: UK and Japanese subsidiaries start their fiscal year in April, the US federal government in October, and Business Central models all of them with accounting periods. Your consolidation report needs the arithmetic underneath those periods: given nothing but the fiscal-year start month, place any date in its fiscal period and find the exact boundaries of the fiscal year it belongs to.

Requirements

Create a codeunit named "Fiscal Period Mapper" with three public procedures:

procedure GetPeriodNo(FiscalYearStartMonth: Integer; TheDate: Date): Integer
procedure GetFiscalYearStartDate(FiscalYearStartMonth: Integer; TheDate: Date): Date
procedure GetFiscalYearEndDate(FiscalYearStartMonth: Integer; TheDate: Date): Date

A fiscal year begins on day 1 of FiscalYearStartMonth and consists of 12 periods of exactly one calendar month each.

GetPeriodNo returns the period TheDate falls in, from 1 to 12: the start month is period 1, the following month is period 2, and the month right before the start month is period 12. With an April start, 2026-04-01 is period 1 and 2026-03-31 is period 12.
GetFiscalYearStartDate returns the first day of the fiscal year containing TheDate. If TheDate's month is on or after the start month, the fiscal year began that same calendar year; otherwise it began the year before.
GetFiscalYearEndDate returns the last day of that same fiscal year — the day before the next fiscal year begins. This is where leap days bite: a fiscal year that starts in March ends on the last day of February, which is February 29 in a leap year and February 28 otherwise — and century years such as 2100 are not leap years.
All three procedures must raise an error when FiscalYearStartMonth is outside 1–12; the error message must contain the exact phrase between 1 and 12.

What the tests check

The tests call your procedures with fixed cases — a January start (periods = calendar months), an April start on the first day of the fiscal year and on both sides of the year-end wrap, February 29, 2024 mapped to its period, an October start probed on, after, and just before its start date, and March starts whose fiscal years end in February 2024 (leap), February 2022 (common), and February 2100 (century year, not leap) — plus randomized start months and dates graded on each of the three procedures, so hardcoding the examples fails. Three more tests pass start months 0 and 13, one per procedure, and expect an error containing between 1 and 12.

Learn More

Hint 1

The period number is pure month arithmetic: how many months past the start month is the date's month, wrapping around December? Note the off-by-one — the start month itself is period 1, not 0, and a month before the start month must land in 7..12, never in a negative number.

Hint 2

For the fiscal year start, the only real question is which calendar year: if the date's month is before the start month, the fiscal year began the year before. Once you know day (always 1), month, and year, building the date is one call.

Hint 3

Never compute February's length yourself — the leap rules, century exception included, already live in the platform's date arithmetic. The fiscal year's last day is exactly one day before the next fiscal year starts, and you can subtract a day from a Date directly (or via CalcDate).

ALBusiness Central 28.5

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