Subtract a number of working days from a date

@atulp Yes the approach should be able to cope with both weekends and holidays occurring within the period you're counting back from. I ended up using two expressions. The first used the workday function to count back a number of days, taking into account weekends, and then it called another expression that used calworkdays to check if, when counting forwards and including holidays, the result returned the original date (or the next workday if the original date was a weekend). This second expression was recursive and called itself if, when counting forwards, the correct date wasn't returned.

Here's the first expression:
=with(
local!startWorkday: caladddays(ri!referenceDate,0),
local!checkDate: workday(local!startWorkday,-ri!days),
local!numWorkDays: calworkdays(local!checkDate,local!startWorkday),
if(
local!numWorkDays=ri!days+1,
local!checkDate,
rule!IWTCIS_getDateByCalWorkdays(ri!referenceDate,local!checkDate,ri!days)
)
)

And here's the second:
=if(
/* Use caladddays with 0 to ensure we compare with a working day */
calworkdays(ri!checkDate,caladddays(ri!referenceDate,0))=ri!days+1,
ri!checkDate,
rule!IWTCIS_getDateByCalWorkdays(ri!referenceDate,ri!checkDate-1,ri!days)
)

This may not meet your needs exactly but should give you a good starting point (it might not be efficient either as it uses recursion but it seemed to work for us and I was nearly going blind from staring at the screen when trying to get this to work so quit trying to optimize it once I got it working).

Note this relies on the holidays being defined in the system working calendar.

@atulp Yes the approach should be able to cope with both weekends and holidays occurring within the period you're counting back from. I ended up using two expressions. The first used the workday function to count back a number of days, taking into account weekends, and then it called another expression that used calworkdays to check if, when counting forwards and including holidays, the result returned the original date (or the next workday if the original date was a weekend). This second expression was recursive and called itself if, when counting forwards, the correct date wasn't returned.

Here's the first expression:
=with(
local!startWorkday: caladddays(ri!referenceDate,0),
local!checkDate: workday(local!startWorkday,-ri!days),
local!numWorkDays: calworkdays(local!checkDate,local!startWorkday),
if(
local!numWorkDays=ri!days+1,
local!checkDate,
rule!IWTCIS_getDateByCalWorkdays(ri!referenceDate,local!checkDate,ri!days)
)
)

And here's the second:
=if(
/* Use caladddays with 0 to ensure we compare with a working day */
calworkdays(ri!checkDate,caladddays(ri!referenceDate,0))=ri!days+1,
ri!checkDate,
rule!IWTCIS_getDateByCalWorkdays(ri!referenceDate,ri!checkDate-1,ri!days)
)

This may not meet your needs exactly but should give you a good starting point (it might not be efficient either as it uses recursion but it seemed to work for us and I was nearly going blind from staring at the screen when trying to get this to work so quit trying to optimize it once I got it working).

Note this relies on the holidays being defined in the system working calendar.