Get Current date in epoch from Unix shell script

Question

How to get the current date value in epoch i.e., number of days elapsed since 1970-1-1. I need solution in unix shell script.

Answer 1

Update: The answer previously posted here linked to a custom script that is no longer available, solely because the OP indicated that date +'%s' didn't work for him. Please see UberAlex' answer and cadrian's answer for proper solutions. In short:

1. For the number of seconds since the Unix epoch use date(1) as follows:

   date +'%s'
   

2. For the number of days since the Unix epoch divide the result by the number of seconds in a day (mind the double parentheses!):

   echo $(($(date +%s) / 60 / 60 / 24))