Editing Metric prefix (section)

==== Time ====
{{see also|Metric time|Orders of magnitude (time)}}

Prefixes for the SI standard unit [[second]] are most commonly encountered for quantities less than one second. For larger quantities, the system of [[minute]]s (60&nbsp;seconds), [[hour]]s (60&nbsp;minutes) and [[day]]s (24&nbsp;hours) is [[Non-SI units mentioned in the SI|accepted for use with the SI]] and more commonly used. When speaking of spans of time, the length of the day is usually standardised to {{val|86,400}}&nbsp;seconds so as not to create issues with the irregular [[leap second]].{{cn|date=November 2022}}

Larger multiples of the second such as kiloseconds and megaseconds are occasionally encountered in scientific contexts, but are seldom used in common parlance. For long-scale scientific work, particularly in [[astronomy]], the [[Julian year (astronomy)|Julian year]] or ''annum'' (a) is a standardised variant of the [[year]], equal to exactly {{val|31557600}}&nbsp;seconds ({{sfrac|365| 1 |4}}&nbsp;days). The unit is so named because it was the average length of a year in the [[Julian calendar]]. Long time periods are then expressed by using metric prefixes with the annum, such as megaannum (Ma) or [[gigaannum]] (Ga).{{cn|date=November 2022}}