Editing Equation of time (section)

== Notation ==
[[File:EquationofTimeandAnalemma.gif|thumb|upright=2.7|Animation showing equation of time and [[analemma]] path over one year.]]

The United States Naval Observatory states "the Equation of Time is the difference ''apparent solar time'' minus ''mean solar time''", i.e. if the sun is ahead of the clock the sign is positive, and if the clock is ahead of the sun the sign is negative.<ref>{{cite web|url=https://aa.usno.navy.mil/faq/eqtime|author=Astronomical Applications Department|title=The Equation of Time|access-date=1 August 2022|website=United States Naval Observatory|publisher=United States Navy}}</ref><ref>{{cite web|url=https://aa.usno.navy.mil/faq/asa_glossary|author=Astronomical Applications Department|title=Astronomical Almanac Glossary|access-date=1 August 2022|website=United States Naval Observatory|publisher=United States Navy}}</ref> The equation of time is shown in the upper graph above for a period of slightly more than a year. The lower graph (which covers exactly one calendar year) has the same absolute values but the [[Sign (mathematics)|sign]] is reversed as it shows how far the clock is ahead of the sun. Publications may use either format: in the English-speaking world, the former usage is the more common, but is not always followed. Anyone who makes use of a published table or graph should first check its sign usage. Often, there is a note or caption which explains it. Otherwise, the usage can be determined by knowing that, during the first three months of each year, the clock is ahead of the sundial. The [[mnemonic]] "NYSS" (pronounced "nice"), for "new year, sundial slow", can be useful. Some published tables avoid the ambiguity by not using signs, but by showing phrases such as "sundial fast" or "sundial slow" instead.<ref name="Waugh"/>