Dynamic formula that splits/distributes revenue a value among various monthly start and end dates

John_Bloggs650 

The function was extracted from a workbook that used a month-based timeline with period start and period end dates (the 1st and 28/29/30/31st respectively).  It could be that would be more use to you.

Some functions:

Addλ = LAMBDA(x, y, x + y);

Timelineλ = LAMBDA(modelStart, duration, [option],
    LET(
        numberPeriods,  duration*MPY,
        counter,        SEQUENCE( , numberPeriods),
        periodEnds,     EOMONTH(modelStart, counter-1),
        periodStarts,   1 + EOMONTH(periodEnds, -1),
        SWITCH(option, 0, periodStarts, 1, periodEnds, counter)
    ));

UniformSpreadλ = LAMBDA(amount, eventStart, [duration],
    LET(
        months, IF(ISOMITTED(duration),1,duration),
        eventFinish,    EOMONTH(eventStart, months - 1),
        withinPeriod,  (modelPeriodBegins# >= eventStart) * 
                       (modelPeriodEnd#    <= eventFinish),
        IF(withinPeriod, amount/months, 0)
    )
);

SeasonallyAdjustedλ = LAMBDA(base, adjustment,
    LET(
      appliedSeasonalityAdj, INDEX(adjustment, MONTH(modelPeriodBegins#)),
      appliedSeasonalityAdj * base
   ));

StepIncreaseλ = LAMBDA(base, ratio, eventStart,
    IF(modelPeriodBegins#<eventStart, base, base*ratio)
);

The book also had a function to accumulate a balance from inflows and outflows and apply interest payment on positive balances but that is well out of scope here.