You have never needed an excuse...
...but it doesn't hurt to have one ;-)

This app will show you the time to the next 4:20 and the associated places. And remember, there are not just one or two 4:20s every day. There are more than 40+ fourtwentys spread over the whole day in all time zones of the earth.

-> 4:20 AM & PM
-> all time zones
-> over 70+ cities & regions
-> considers time shift
-> optional notifications

Enjoy!