Converting epoch second to date time, and vice versa

epoch.mk

EPOCH = 0
DATE = 1970-01-01 00:00:00 JST

all:

now:
	date
	date +%s

date:
	date -d @$(EPOCH)

epoch:
	date -d"$(DATE)"
	date -d"$(DATE)" +%s

.PHONY: all now date epoch