Adding and subtracting dates in ColumnExpressions

I am currently manipulating a set of dates in a single table with different “categories of dates”. I am currently identifying a marker in one column (e.g. LY_YTD_Act or TY_YTD_Act) and populate a new column with a date plus or minus another date to interpret these markers.

I thought column expressions may do the trick here - I set a base date using a flow variable from a quick form and then assign the date value. Problem is that I am unable to increase/decrease the date value relative to the base value and can’t find an appropriate syntax for it.

My initial ColumnExpression syntax is:
if (column(“ValueType”) == ‘TY_YTD_Act’) ValueDateTime = variable(“ValueDate”);

I now only need to manipulate the date e.g.
if (MARKER_1) then ValueDateTime = FlowVariableDate + [year/month/day]; //pseudo code

Any advice is appreciated.

Hi there!

Not sure I understand. Maybe an example?