Systemd calendar expression helpers.
See Systemd.Calendar.daily_at/1.
Systemd.Calendar.daily_at/1
See Systemd.Calendar.monthly_at/2.
Systemd.Calendar.monthly_at/2
See Systemd.Calendar.weekly_at/2.
Systemd.Calendar.weekly_at/2
@spec daily_at(String.t() | Time.t()) :: String.t()
@spec monthly_at(pos_integer(), String.t() | Time.t()) :: String.t()
@spec name(atom() | String.t()) :: String.t()
@spec weekly_at(atom() | String.t(), String.t() | Time.t()) :: String.t()