title: Trying to get meaningful timestamp while subtract it with actual time of Linux?
body: <p>a=<code>date '+%H'</code>. when i do a-1, if the time is 00:00 it will give me -1 which is not i want. I trying to show it as 23:00.</p>
  
  <p>Could you please help me with working code?
  Thanks in advance :)</p>