The numbers do not move. 1400 is always 2:00 PM, 2200 is always 10:00 PM, and 0000 is always the first minute of the day. What shifts twice a year is the offset between those numbers and the Sun, and that shift changes the military zone letter attached to a location even though the clock on the wall looks identical.
Military time measures the day. Daylight saving time is a political decision about which number sits at high noon. When a government alters that decision, the numbers on your clock jump, but the system for reading them does not budge. The only question is which time zone letter the local time maps to, and that letter can flip overnight.
Zulu time ignores the politicians
Zulu time, the military name for UTC+0, ignores daylight saving entirely. Always. When New York is on Eastern Standard Time, it sits at UTC-5, zone R. When New York springs forward to Eastern Daylight Time, it becomes UTC-4, zone Q. The local wall clock still says 1400 in both seasons, but the instant it marks is different by one hour.
That is why aviation, the military, and global IT operations default to Zulu. A flight plan filed for 1430 Zulu is unambiguous in January and July alike. File the same plan for 1430 local time and everyone has to ask: "Which local time, and which season?"
The lettered military zones (A through M and N through Y, skipping J) are tied to fixed UTC offsets. Zone A is UTC+1, zone B is UTC+2, all the way to zone M at UTC+12, then the negative offsets from N at UTC-1 down to Y at UTC-12. Zone Z is Zulu, UTC+0. Zone J, Juliett, is the outlier: it means the observer's local time, whatever that happens to be.
The letter belongs to the offset, not the map
Take a military base on the US East Coast. In January, during standard time, the local offset is UTC-5, zone R. A log entry written at 0600 local time is also 1100 Zulu. The date-time group might read "0600 R."
In July, during daylight time, the offset moves to UTC-4, zone Q. The same 0600 local time is now 1000 Zulu. Same base, same geographic coordinates. The Sun still rises at roughly the same local clock time. But the relationship between local time and Zulu time has shifted by one hour, and the correct zone letter has shifted with it.
Here is the trap: someone who says "R time" in July is using the wrong letter for that location. The letter belongs to the offset, not the geography. A unit that forgets the shift and keeps the old letter will be off by one hour from everyone else. This is exactly why the military leans on Zulu for anything crossing time zones or seasons. Lettered zones identify an offset. They are not a substitute for stating the offset or using Zulu.
In the United States, clocks spring forward on the second Sunday in March and fall back on the first Sunday in November. On those nights, the local clock jumps from 0159 to 0300 in the spring, skipping 0200 entirely. In the fall, the clock drops from 0159 back to 0100, repeating the 0100 hour. Military time handles this without complaint. 0200 is 0200. 0300 is 0300. The numbers do not care about the Sun.
The 24-hour clock removes one whole category of error
The real danger of a daylight saving shift is not the lost hour of sleep. It is the ambiguity in records that use 12-hour time. A medication scheduled for 12:00 AM on the night of a fall-back shift is genuinely ambiguous: 12:00 AM occurs twice. A nurse charting in military time writes 0000 for midnight, and there is no second 0000 in the same day. The repeated 0100 hour in the fall is handled by writing the date alongside the time, standard practice in any military or medical log.
The Joint Commission has pushed US hospitals toward 24-hour charting for exactly this reason. Documented medication errors from AM/PM confusion, particularly around midnight dosing, drove the recommendation. Military time does not erase the confusion of a repeated hour, but it does eliminate the far more common confusion between 12:00 AM and 12:00 PM, which has caused countless missed doses and missed flights.
The same logic holds for computer systems. Server logs in UTC ignore daylight saving time completely. A cron job scheduled for 0300 UTC runs at the same instant every day of the year. Schedule it for 0300 local time and it drifts by one hour twice a year, and your logs show the jump. The standard advice for any globally distributed system: store time in UTC, convert to local time only for display.
The rules are not permanent
In 2018 the European Parliament voted to end mandatory seasonal clock changes by 2021, but the proposal stalled in the Council of the European Union. As of 2026, no final decision has been made. If the EU ever does abolish DST, each member state will pick its permanent offset, and military zone letters across Europe will adjust accordingly.
In the United States, the Sunshine Protection Act (which would make daylight saving time permanent) passed the Senate in 2022 but stalled in the House. If it becomes law, the US would shift one zone letter eastward permanently. Eastern Daylight Time would become the year-round standard: the East Coast would sit at UTC-4 all year instead of alternating between UTC-5 and UTC-4. The zone letter would stop changing in March and November, ending the seasonal letter shift for the entire country.
Neither proposal touches military time itself. The 24-hour clock is a counting system. Legislation does not change it. What changes is the offset, the zone letter, and the relationship between local time and Zulu time.
Handle the shift without getting burned
Schedule anything across a daylight saving shift in Zulu time. Write the date and the offset. A date-time group like "0600 R JAN 25" is unambiguous because it names the offset. Write only "0600 local" and you force the reader to know the season, the location, and the current DST rules. That is a lot to assume.
Reading a military log from a shift night? Check the date-time group carefully. A fall-back shift means the 0100 hour happens twice. Without a zone letter or a date, you cannot tell which 0100 is meant. With a zone letter, the ambiguity disappears.
Writing software? Store time in UTC. Convert to local time only at the edge, for display. Never write a cron job that depends on local time unless you understand the DST rules for your region, including the ones that might change next year.
The next shift is the fall-back on the first Sunday in November. Clocks in most of the United States drop from 0200 to 0100. For military time users, nothing about the numbers changes. 0200 is still 0200. But the zone letter shifts, the Sun rises an hour earlier relative to the clock, and anyone coordinating across time zones has one more reason to be grateful for Zulu.