Hledger.Data.Period
periodAsDateSpan
dateSpanAsPeriod
simplifyPeriod
isLastDayOfMonth
isStandardPeriod
showPeriod
periodStart
periodEnd
periodNext
periodPrevious
periodNextIn
periodPreviousIn
periodMoveTo
periodGrow
periodShrink
mondayBefore
yearMonthContainingWeekStarting
quarterContainingMonth
firstMonthOfQuarter
startOfFirstWeekInMonth