fix: Bring back `Sunrise` and `Sunset` daily variables

[leo-210]

The commit e65f2d4 removed the Sunrise and Sunset variables because they caused problem.

They were removed because unlike all other daily variables, that are either of type Int or Float, Sunset and Sunrise are of type Time.

[leo-210]

One way to fix it would be to convert the date in unix time, so that it is an integer.
If there are no better solutions, I think this could be an acceptable one.

Maybe, instead of keeping the seconds or milliseconds since 1970 (unix time), I could do milliseconds since midnight. The only problem is that, to my knowledge, it's not really a common way to store time, and might cause some confusions.

Another way would be to put these variables in their own fields, separated from the rest (e.g. a dates field, and the rest in measurements). But this is not very elegant imo.