-- Seconds since 1970-01-01 00:00:00 UTC
local now = os.time()
-- No argument: the local time as text
local now_text = os.date()
-- A format picks the parts, here the date only
local today = os.date("%Y-%m-%d")
-- Only two zones: local and UTC ("!" in front)
local utc_date = os.date("!%Y-%m-%d", now)
print("now = " .. now)
print("now_text = " .. now_text)
print("today = " .. today)
print("utc_date = " .. utc_date)