Get System Date Time
dtt_sys_date_time(tz = dtt_default_tz())
A string of the time zone.
A floored POSIXct scalar.
Other sys:
dtt_sys_date()
,
dtt_sys_time()
if (FALSE) {
dtt_set_default_tz("UTC")
dtt_sys_date_time()
dtt_set_default_tz("Etc/GMT+8")
dtt_sys_date_time()
dtt_sys_date_time(tz = "UTC")
}