We get a lot of threads asking how to find yesterday's date. Or how to find the date exactly 2 months into the future, etc.

I wrote a script called datecalc that can do virtually any kind of date arithmetic. datecalc is my favorite solution. But there are several other solutions to consider. Here are some other threads....

Date function question
This thread has a perl solution, an adb solution, and an early script written by me.

Getting yesterday DATE
The last post in this thread mentions altering the TZ variable. I don't think this is very portable nor general, but it is an interesting option.

Subtracting Two months from date
This thread mentions the advanced options available with the GNU date command.

date manipulation
This thread has another perl solution.

Date Logic
Whoa... This thread has one post that suggests using a database.

Date calculation script
Here is another shell script.

get yesterday in yyyymmdd format
Review of some of above techniques by folks who didn't read this FAQ.

And a few more threads that you may find interesting....

How to find Previous date and Coming date
how to get number of seconds
Date Substraction
Calculte date time
Add Date
Julian Date
building text file with calendar dates
convert date in lilian format for shell (AIX)
Yesterday's date function
Calculating the day of the week
validating dates
Time & Date Manupulations
calcuate the week number of a given date
Keeping the format ...
Getting sysdate - 2 by an unix command
how to get month last date in unix
How to get the weekday of the given date?

And some interesting magazine articles:

Date Arithmetic with the Shell
Date arithmetic, Part 1
Date arithmetic, Part 2
Date arithmetic, Part 3

And a interesting web site:

Hermetic Systems: Calendars, Encryption, Astronomy, Prime Numbers and More


This thread shows how to do time arithmetic using the GNU date program.