date - How to get last day of last month in unix

Question

I have the requirement to get the last date of the last month.

For today the last months last day is 30 (April).

Answer 1

this should work if you have gnu date:

1 day ago <month> 1

<month> here is current month, for example

kent$  date -d'1 day ago may 1' 
Tue Apr 30 00:00:00 CEST 2013

another example, find the last day of the month before July:

kent$  date -d'1 day ago july 1'
Sun Jun 30 00:00:00 CEST 2013

note that, the timestamp was set to 00:00:00.