add year, month, day to unix epoch timestamp
- supports year, month, day in positive and negative integers
- supports seconds, milliseconds or nanoseconds timestamps
- all datetimes in UTC
curl https://raw.githubusercontent.com/Luke31/epochadd/main/epochadd --output ~/bin/epochadd
epochadd <inputepoch> <years> <months> <days>
Doesn't work for dates after 2286-11-20 17:46:39 (epoch 9999999999)