Basic Trope: Magic uses dramatic units of time, for deadlines, for things to happen, for how long things take.
Pascal is born to a family of werewolves on Easter, and is unaffected by the shapeshifting curse.
A spell to increase the crops must be cast while the moon is waxing.
A warlock casts a curse at midnight, with the moon new, to increase its power.
Anyone who offends the dragon Breakspeare must serve it for a year and a day to expiate.
Exaggerated: Any event's effects, including how long it lasts, are determined by when it happens, and people compile long lists of significant times, create very accurate timepieces, and do not so much as do the laundry or cook a meal without checking for the phase of the moon and where the sun is.
Downplayed: Certain spells are renewed annually because it's safer than letting them wear off.
Justified: the dramatic dates are linked to magic, such as Easter being a time of heavy white magic influence, with lycthanropy being black magic.
Subverted: Wizards always perform rites on solstices and equinoxes, but this is to make them look rare and difficult to do, to charge more money.
Double Subverted: When some wizards try to undercut the others by using other days, they find the rites are weaker.
Parodied: Bob has a curse that makes him go Ax-Crazy every monday, and everybody agrees it makes mondays more interesting.
Zig Zagged: ???
Averted: There are more mundane measurements such as hours, or similar to weather patterns.
Enforced: It's a story symbolizing Christan belief.
Lampshaded: "Let's see, Valentines is coming up, maybe you could cast a love spell on him?"
Invoked: Bob, a devout Christan, wants to associate miracles with Easter.
Exploited: James, a Magnificent Bastard, intentionally has the dates of holidays changed in order to screw up practicing spellcasters.
Defied: Hieronymous casts, whenever he likes, a spell that his master told him should only be cast on Midsummer's Eve.
Implied: Events in a novel always take place when the moon is full.