Set it up in Slack and HipChat, or give it a try below:

/tz
↵  
  • 10:00 am CET in Stockholm is 4:00 am EST for you
  • Stockholm is 6 hours ahead of you
  • 10:00 am KST in Seoul is 8:00 pm EST the previous day for you
  • Seoul is 14 hours ahead of you
  • 10:00 am CET in Stockholm is 6:00 pm KST for Seoul
  • Stockholm is 8 hours behind Seoul

Examples: