Are you wanting to perform the Actions at Specific Times of the Day (at the Same time each Day)?
Or do you want to perform the Actions based from when the Particle Device was last Reset ?
The TimeAlarm Library is what you want for Specific Times of the Day, see Post 26:
https://community.particle.io/t/help-with-setting-photon-schedules/41267/26
Millis() is what you use for “Runtime” since Reset.