Revision as of 14:02, 19 January 2025 edit VulcanSphere (talk \| contribs) Extended confirmed users 22,155 edits m Changing short description from "Extra second inserted to keep civil time in sync with the Earth's rotation" to "Extra second inserted to keep civil time in sync with Earth's rotation" Tag: Shortdesc helper ← Previous edit		Revision as of 14:10, 19 January 2025 edit undo VulcanSphere (talk \| contribs) Extended confirmed users 22,155 edits →Issues created by insertion (or removal) of leap seconds Tag: Visual edit Next edit →
Line 276: ==Issues created by insertion (or removal) of leap seconds== [[File:ChronyControl screenshot.webp\|thumb\|upright=1.5\|Screenshot of [[Chrony]]Control on [[macOS]], showing an insert second announcement by NTP on 30 June 2015.]] ===Calculation of time differences and sequence of events=== To compute the elapsed time in seconds between two given UTC dates requires the consultation of a table of leap seconds, which needs to be updated whenever a new leap second is announced. Since leap seconds are known only 6 months in advance, time intervals for UTC dates further in the future cannot be computed. Line 284: ===Implementation differences=== Not all clocks implement leap seconds in the same manner. Leap seconds in [[Unix time]] are commonly implemented by repeating 23:59:59 or adding the time-stamp 23:59:60. [[Network Time Protocol]] (~~SNTP~~NTP) freezes time during the leap second,<ref>{{Cite web \|date=10 February 2010 \|title=NIST Internet Time Service (ITS) \|url=https://www.nist.gov/pml/time-and-frequency-division/time-distribution/internet-time-service-its \|website=NIST}}</ref> some time servers declare "alarm condition".{{citation needed\|date=October 2019}} Other schemes ''smear'' time in the vicinity of a leap second, spreading out the second of change over a longer period. This aims to avoid any negative effects of a substantial (by modern standards) step in time.<ref>{{citation\|rfc=7164\|author=Kevin Gross\|title=RTP and Leap Seconds\|date=March 2014}}</ref><ref name=google-smear /> This approach has led to differences between systems, as leap smear is not standardized and several different schemes are used in practice.<ref>{{cite web \| website = Bureau International des Poids et Mesures \| url = https://www.bipm.org/documents/20126/77823803/INTRODUCTION-DRAFT-RESOLUTION-D.pdf/62f31b32-bfe4-969f-5d29-1dc08cc907bb?version=1.2&t=1669373890355&download=true \| title = Draft Resolution D: 'On the use and future development of UTC' \| last1 = Dimarcq \| first1 = Noël \| last2 = Tavella \| first2 = Patrizia \| date = 17 November 2022 \| page = 7}}</ref> ===Textual representation of the leap second===

Leap second: Difference between revisions