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Comment by briffle | Hacker News Reader

My 2015 pickup has a stereo/setup that can get Satellite radio, GPS signals for the mapping program (not activated on mine), regular radio, and a 4G LTE hotspot.

But what really, really annoys me, is I have to push buttons on the screen to update/fix the time.. How the hell does it not have NTP, or get a radio signal, etc?

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Our 2011 Lexus CT200h (no longer with us I'm sad to say) would set time via GPS. I don't understand why every car doesn't do this (especially if it has navi, which requires the GPS chipset regardless).

Especially since the GPS signal has the time in it... likely it is to avoid issues with people claiming it is running fast/slow, or changing timezones.

Only the GPS time value has never had any leap seconds applied to it. So it's almost 20 seconds ahead of UTC. Which is probably "good enough" for a clock in a car.

It seems unlikely that the GPS receiver is hardwired directly to the clock display in the dashboard. There's probably some code running somewhere in the middle. So it should be easy enough to make the leap second correction there, and to keep it up to date through routine updates.

GPS includes the offset between GPS time and UTC so that receivers can convert to UTC if they want to.

This offset is limited to 255 seconds though.

https://en.wikipedia.org/wiki/Global_Positioning_System#Leap...

> This offset is limited to 255 seconds though.

Given that leap seconds have been added at a rate of approximately 1 every 1.6 years, we are still good for another 376 years.

Don't forget that they can be negative leap seconds too! It hasn't happened yet but it is expected.

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