Are the time measurements (4 mil from sunset to nightfall) fixed clock-hours or seasonal hours?

ShabbatOnset of Shabbat

Synopsis

The Pri Megadim holds the 4 mil are fixed hours. The Minchat Kohen and Magen Avraham (citing Maharil) hold they are seasonal hours that vary with day length.

Late Acharonim
Lenient
Strict
Lesser cited
Major authority

Discussion

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