Adding a leap second is referred to as a "leap second insertion". If a direct mapping doesn't exist, it's the last representable value before the insertion of a leap second in the case that t represents a point in time when a leap second was inserted. The sys_time set to the equivalent point in time as t. Static method that converts a utc_time to a sys_time. If a direct mapping doesn't exist, the time_point during a leap second insertion and the last representable value of sys_time before the insertion of the leap second, is returned. templateĪ utc_time set to the time that most closely approximates the sys_time t. Static method that converts a sys_time to a utc_time. Indicates whether the clock type is steady. Used to represent a time_point for this clock.Ī synonym for using utc_seconds = utc_time Ī synonym for template using utc_time = time_point Represents a time_point for a utc_clock. It represents the time in seconds (100 nanoseconds) between each tick in the duration.Ī synonym for the type ( long long) used to represent the integral units in this clock's utc_clock::duration.Ī synonym for time_point. Microsoft's implementation defines this as a synonym for system_clock::period. It represents a duration of time measured in units of 100 nanoseconds. It also includes the sum of all the leap seconds between Januand the specified duration. Gets a leap_second_info that indicates whether the supplied time specifies a time when a leap second was inserted. Parse a utc_time from the given stream using the specified format. Given the insertion of another 27 leap seconds since then, UTC time is currently 37 seconds behind TAI (atomic clock) time. 10 seconds were added in 1972 to TAI time to accommodate for the leap seconds that had accumulated by that point. UTC time, by definition, starts out 10 seconds behind TAI (atomic time). Historically, leap seconds have been added on June 30 or December 31.
When a leap second is inserted, the time, as it nears midnight, proceeds from 23 hours 59 minutes 59 seconds to 23 hours 59 minutes 60 seconds (the inserted leap second), and then to 0 hours 0 minutes 0 seconds (midnight). The International Earth Rotation and Reference Systems Service (IERS) determines when a leap second will be added.
A leap second adjustment keeps UTC tracking time within a second of the average length of a day.Īs of this writing, 27 leap seconds have been added since the practice of inserting leap seconds began in 1972. That's because the earth's rotation speed is irregular, and in general is slowing down over time by about one second every 1.5 years (although sometimes the earth's rotation speed increases). There's a discrepancy between the time kept by atomic clocks, and the time kept by tracking the rotation of the earth. However, a leap second is occasionally added to UTC time to keep the difference between UTC time and UT1 (solar time) within +- 0.9 seconds. The rate of UTC time is based on International Atomic Time (TAI) which uses atomic clocks to track time. This clock accounts for leap seconds and is the basis for civil time around the world. This clock measures time since 00:00:00 UTC on Thursday, January 1, 1970. Local time is adjusted from UTC time depending on your time zone. A clock for Coordinated Universal Time (UTC) which is sometimes popularly referred to as Greenwich Mean Time (GMT) or Zulu time.
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