Get Current date in epoch from Unix shell script

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

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))
   

The Unix Date command will display in epoch time

the command is

date +"%s"

https://linux.die.net/man/1/date

Edit: Some people have observed you asked for days, so it's the result of that command divided by 86,400