Standard Time, UTC, and Time Zones in Aviation

061-05-02Pablo Asensio Martínez2026-04-012 min

Time management is fundamental in aviation to ensure safety and global coordination. Below, we explain the key concepts for understanding how time works in different regions and how it affects air navigation.

Difference between Standard Time and UTC

Standard Time (ST) is the local time used in a specific geographic region. This time is established by the government or competent authority of each country and depends on the time zone in which that territory is located. Countries use standard time to align noon with 12:00 and midnight with 00:00, seeking to take advantage of light and dark cycles.

On the other hand, UTC (Coordinated Universal Time) is the global reference for time. Unlike local time, UTC does not change with daylight saving time and serves as the basis for all time zones in the world. In aviation, UTC is the standard used for air traffic control, flight plans, and weather forecasts, in order to avoid confusion between different time zones.

Conversion Rules

To make precise time calculations and avoid errors, the golden rule in aviation is to always work through UTC.

  • To obtain UTC from Standard Time, the opposite correction to that of the time zone is applied (for example, if the local time is UTC+10, we subtract 10 hours).
  • Precise information about time conversions is officially published in the Air Almanac.

Daylight Saving Time

The main objective of Daylight Saving Time (DST) is to make better use of daylight, transferring one hour of light from morning to afternoon.

  • When daylight saving time is applied, one hour must be added to Standard Time.
  • This means that darkness arrives later on the clock. To return to standard time in autumn, that additional hour is subtracted.
  • In the tropics and near the equator, where day and night duration is similar throughout the year, the time change is generally not used.

Global Navigation and the International Date Line

Because the Earth rotates from West to East, time toward the East always goes ahead of time toward the West. When traveling around the world, pilots and travelers must adjust their clocks and calendars according to the direction of flight:

Traveling West (Westerly):

  • The clock is set back one hour for every 15° of longitude.
  • When crossing the International Date Line, one day must be added (advance the date 24 hours).

Traveling East (Easterly):

  • The clock is advanced one hour for every 15° of longitude.
  • When crossing the International Date Line, one day must be subtracted (go back the date 24 hours).

In summary: when crossing the date line westward you gain a day, while when crossing it eastward you lose a day on the calendar.