[Tagging] Day/night speed limits

[Tod Fitch]

There are a number of roads in Arizona, and perhaps elsewhere, that have different speed limits for night vs day. You can see some examples with this search [1]. These are not based on wall clock time as they vary with the time of sunrise and sunset. Suggestions on how to tag the speed limits on the roads affected?

[1] https://duckduckgo.com/?q=arizona+day%2Fnight+speed+limit+sign&bext=msl&atb=v45-6&iax=1&ia=images

Thanks!