To determine the length of a day, you need to know the axial tilt, the latitude of where you want to know the length of a day, and the calendar day you want to know the day length of.
To determine time of sunrise and sunset, you additionally need to know either the absolute longitude, or at least the relative longitude within the band for which the time zone applies (in fantasy world terms, there would have to be a location that is the standard to which regional times are defined). In a world without standards-setting bodies, this could be very chaotic, where a large, powerful realm might have its capital govern the time standard and every other location within the sway of this realm would have its time anchored to that. So, in the very east of such a realm (assuming counterclockwise rotation of the planet relative to the ecliptic), the sun might rise at 3AM (using an earth-like time scale), while it might rise at 12PM in the very west end (for a large realm, e.g.). Remember, even on earth, there are some locations that observe a daylight savings time and some that don't; locations where there are 30 minute time zones and hour time zones; and locations where time zones are widely distorted from a strictly longitudinal basis for the sake of convenience [usually so a small country does not need to have separate time zones].
Another common practice in fantasy cultures would be to reset your chronometer (mechanism would vary depending upon whether the chronometer is a sundial, hourglass, or mechanical device) to some standard reticle value when the sun first touches the horizon (or when the first cock crows, the first cricket chirps, or some other observable phenomenon).
And this all assumes there is only one sun in the system.
If Realmworks is attempting to capture such aspects within its calendar system, it is no wonder it is taking so long to develop.