How to create a countdown but not with specified timezone nor date

First add the command, you can make it anything.
!commands add !respawn -a=__respawn__ $(query)

Then add a set command. Making sure to replace [SetTimezone] with the timezone of your choice.
!commands add !resetrespawn -ul=moderator -a=!commands edit !respawn $(query) [SetTimeZone]

Fix
Adding a new command in order to pass the saved time to a countdown
!commands add __respawn__ Time Remaining: $(countdown $(query))

To Set:
!resetrespawn 5:00:00 PM to set to countdown until 5pm

Sadly Nightbot can’t add time to advance it 8 hours forward automatically so that manual time setting would be needed, however you don’t have to enter the Timezone every time.