title: Regular expression to allow only the valid time offset values
body: <p>I am looking for a regular expression which allows only the time offset values.</p>
  <p>I have used:</p>
  <pre><code>^(?:[+-](?:2[0-3]|[01][0-9]):[0-5][0-9])$
  </code></pre>
  <p>The ONLY strings I need to match:</p>
  <pre><code>-12:00
  +14:00
  -11:00
  -10:00
  -09:30
  -09:00
  -08:00
  -07:00
  -06:00
  -05:00
  -04:00
  -03:30
  -03:00
  -02:00
  -01:00
  00:00
  +01:00
  +04:00
  +03:30
  +03:00
  +02:00
  +04:30
  +05:00
  +05:30
  +05:45
  +06:00
  +06:30
  +07:00
  +08:00
  +08:45
  +09:00
  +09:30
  +10:00
  +10:30
  +11:00
  +12:00
  +12:45
  +13:00
  +14:00
  </code></pre>
  <p>Please check <a href="https://regex101.com/r/lqcgRl/1" rel="nofollow noreferrer">here</a> for what I have tried so far, and the values I want it to allow.</p>
  <p>It works fine for the all the values except for 00:00.
  Also, it allows some extra values such as <code>-19:30</code> <code>+23:00</code> <code>22:30</code> <code>21:00</code> which should not be allowed.</p>
  <p>I want it to allow only those values which have been mentioned in my aforesaid link.</p>