Federal law sets the rule: clocks go forward one hour at 2 a.m. on the second Sunday of March and back one hour at 2 a.m. on the first Sunday of November.
2026: daylight saving time ends Sunday, November 1, at 2 a.m.
2027: it begins Sunday, March 14, and ends Sunday, November 7.
In fall the sky gets dark an hour earlier by the clock overnight. Sunset on October 31, 2026 is 5:52 PM; the next evening it is 4:51 PM. In spring it jumps the other way: on March 13, 2027 sunset is 5:53 PM, and on March 14 it is 6:54 PM. Any light set to come on at a fixed clock time is suddenly an hour early or an hour late against the sky.
Mechanical dial timer: it has no idea what day it is. It keeps turning, but after the change its dial reads an hour off the wall clock until you rotate it. Its on and off pins never follow sunset either, so it needs moving every few weeks as well.
Digital timer with fixed times: some have an automatic daylight saving setting, some do not. If yours does not, change its clock by hand.
Older timers with built-in daylight saving: NIST notes that clocks built before the current rule took effect in 2007 may change on the old dates, waiting until April in spring. If a timer still jumps a few weeks late, turn its automatic setting off and adjust it yourself.
Astronomic timer: it works out sunrise and sunset from your location and the date, so it follows the seasons. It still needs the correct date, time zone and daylight saving setting to get that math right.
Photocell or dusk-to-dawn: it reads the light and has no clock, so the time change does not touch it. It cannot switch off at a chosen hour, though, and shade or a nearby streetlight can fool it.
Smart plug, bulb or app-run system: most take the time from the internet and the time zone from the account or phone. Sunset-based schedules shift on their own. Fixed-time ones keep the same clock time, which may no longer suit the sky.
The evening of the change, step outside at dusk and see which lights are on.
Turn every mechanical dial to the correct time.
Compare each digital timer with your phone.
In fall, move any fixed on-time about an hour earlier. In spring, move it about an hour later.
Open each lighting app and confirm the next scheduled on-time looks right.
Wipe dust or pollen off photocell sensors while you are out there.