Editing Time signal (section)

{{short description|Signal used as a reference to determine the time of day}}
{{Use dmy dates|date=January 2020}}
{{broader|Time standard}}
[[File:Time clocks-1905.jpg|frame|These automatic signal clocks were [[synchronization|synchronized]] by [[telegraphy]] in 1905 before the widespread use of radio]]
A '''time signal''' is a visible, audible, mechanical, or electronic [[signal]] used as a reference to determine the [[time of day]].

[[Church bell]]s or voices announcing hours of [[prayer]] gave way to automatically operated [[wikt:chime|chime]]s on public [[clock]]s; however, audible signals (even signal guns) have limited range. Busy [[Port|seaports]] used a visual signal, the dropping of a ball, to allow mariners to check the chronometers used for navigation. The advent of electrical [[telegraph]]s allowed widespread and precise distribution of time signals from central observatories. [[Railway]]s were among the first customers for time signals, which allowed synchronization of their operations over wide geographic areas. Dedicated radio time signal stations transmit a signal that allows automatic synchronization of clocks, and commercial broadcasters still include time signals in their programming.

Today, global navigation satellite systems ([[GNSS]]) radio signals are used to precisely distribute time signals over much of the world. There are many commercially available [[Radio clock|radio controlled clocks]] available to accurately indicate the local time, both for business and residential use. Computers often set their time from an [[time server|Internet atomic clock source]]. Where this is not available, a locally connected GNSS receiver can precisely set the time using one of several software applications.