I think Google Calendar is brilliant however
one type of repeating event it does not support is the last working day of the
month. There is the option to import a custom ICS file though and within the
specification of that file format you can get pretty much close to last working
day (there may be some exceptions where this doesn’t work, such a bank holidays
but it is close enough).
Create a new file, ie
last-working-day.ics and put this inside it:
SUMMARY:Last working day
DESCRIPTION:Repeating last working day event
Save that and then import into Google Calendar
and it’ll create you a new event that repeats on the last working day of the
month. If you need help importing into Google calendar then see this page in Google’s help docs.