Most people should set their modes to All, to do the same thing every day, since you can't set different programmes for each day.
As for the time, it's best if you imagine a 24 hour clockface.
If you want the room temperature to be warm during the day but cooler when you go to bed at night
In this example we set desired temperature on the Main Menu to 22 °C. This is our "normal mode". We set Night Mode to 17 °C, starting at 22:00 and ending at 06:00 when we get out of bed. At 06:00 the desired temperature will revert to the 22 °C we set on the Main Menu. We do not set Day Mode.
If you go out in the morning and come back later in the day
Night Mode is set as before but we also use Day Mode. We set Day Mode to 10 °C to keep off the chill, starting at 09:00 when we leave, ending 15:00 when we get back. In the times between Day and Night Mode, the desired temperature reverts to 22 °C.
If your programmes don’t work properly
If you set Night Mode and Day Mode to start/end at exactly the same time, they will conflict. There's also no reason to set Night Mode and Day Mode back to back. Your programme should have an hour or so in "normal mode" between Night and Day Mode, otherwise you don't need all three modes.
Finally, don't forget to set the clock.