Had a power cut three months ago. Set my oven, my microwave and alarm clock to match the time on my phone. After setting them they would have all been within 1 minute of each other roughly.
Three months on, at the time of writing this, my phone reads 10:10, oven 9:56, microwave 10:02 and digital clock 10:11.
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The clock in each machine is designed around a resonator – a small device which vibrates and its vibration is measured and counted to keep time. This is much like the pendulum in a clock.
Now these things are precise. Higher quality ones can get very precise. They are not, however, perfect, and every one will be cut slightly different. A different cut means a different frequency, and a different frequency means that one will count faster than another.
They all run with their own “internal clock”, which on cheap models is a simple quartz.
Quartz, like any other component, has variations, which lead to this.
There are ways to sync stuff well, the first being to use better “quartz” with lower spread, and another to use a syncing signal which is what your phone does. A combination of both can result in syncing systems to the nanosecond (i designed and built this for my job).
But it costs money, so on cheap appliances that do not need to be that much accurate, you wont find them.
In addition to the other excellent explanations, it might interest you to know that computers like desktops and smartphones regularly update their internal clocks to stay in sync, ultimately getting their updates from some very very expensive and precise mechanisms run by major governments. If that update mechanism stops working it causes problems for the computers when they try to securely communicate with each other after their clocks drift out of sync
Because that’s how accurate clocks are over time. Quartz clocks, even.
Many electrical appliances rely on the 50/60Hz oscillation of the mains power they use, and that’s not particularly accurate either.
This is why timekeeping was always difficult in the past.
Your phone or PC stays accurate because it queries NTP servers on the Internet – servers that monitor their timing to within nanoseconds and are syncing themselves over NTP to atomic clocks (either in labs, ground stations or on GPS satellites which need accurate clocks, or to radio stations like the MSF Rugby signal in the UK and it’s equivalents worldwide, which pulse based on an maintained atomic clock). Microsoft operate an NTP server for Windows users, specifically to solve this problem.
This is just how inaccurate timing is, generally. If you’re not synced to some reliable time source you can easily lose or gain minute or more a day.
It’s why I run an NTP server. It’s why all my equipment is synced to that NTP server. It’s why my alarm clock is MSF. It’s why the wall clock in my house is MSF. It’s why my car is synced to the GPS time. It’s why I wear a watch that syncs to my phone’s time. And why I don’t have anything that isn’t synced (e.g. I do not have a clock on my microwave or oven), because it being the wrong time drives me mad.
Not because I need to have my life synced to within a fraction of a second, but just because it bugs me that I’m either always adjusting clocks, or they are 5 minutes out (so my timing to get to work is screwed up a little), or when the power goes off or the daylight savings changes occur that I would have to go around resetting them all.
Everything in my house is always to within a second of each other, and they all automatically reset after power-off or a time change.
That is not normal and insane drift. It’s possible you have dirty electricity at your house.
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