I am getting a syntax error and couldn't able to figure out the solution.

Error:
$ sudo ./service_account.sh

List of user accounts with password information
===============================================
Thu May 18 12:34:15 EDT 2017

Legend: M=Minimum password age W=Warning in days before exp
Dis=Account Disabled
------------------------------------------------------------------------------------------
Username |Full name |UID |LastChange|M|Max |W|Passwd Exp|Dis |Acct Exp
----------|-------------------------|-----|----------|-|-----|-|----------|----|----------
./service_account.sh: line 54: 17304 + : syntax error: operand expected (error token is "- ")

Welcome to LQ!
When did it stop working?
When did it last work?
When was it last run successfully?
Who authored service_account.sh?
Have you looked at line 54 of service_account.sh?
Have the correct user/env ?

Please let us know.

When did it stop working?
I tried it today first time.

When did it last work?
N/A
When was it last run successfully?
N/A
Who authored service_account.sh?
I have a ownership to rwx
Have you looked at line 54 of service_account.sh?
I saw the scrip and that line is doing a subtracting
pass=$(( $now - $a ))

Have the correct user/env ?
Yes