My Aeon at work gains a second every 3 months. I reset it at the DST changes.

I haven't looked at the RTC chip pinouts but perhaps if you were THAT concerned about it, you might be able to change bump it forward or back by one second.

WOW! that inaccurate huh!

Read this I found to get an ideal of how accurate this is:

Crystal Clock accuracy is defined in terms of ppm or parts per million and it gives a convenient way of comparing accuracies of different crystal specifications.

.

The following headings give practical calculations showing the typical errors you will encounter when using a clock of a specific type with a specific accuracy.

How good is a 1% accurate clock ?

If you look at a day's worth of timekeeping then you have 24 x 60 x 60 = 86400 seconds in a day. So the maximum error after a day has passed is 1% of 86400 = 864 seconds = 14 minutes!

How good is a typical crystal ?

A typical crystal has an error of 100ppm (ish) this translates as 100/10e6 or 0.001% (its the same number expressed as a percentage). So the total error on a day is 86400 x 0.01%= 8.64 seconds per day so in a month you would loose 30x8.64 = 4.32 minutes per month.

How good is a watch crystal ?

A watch crystal has an error of 20ppm (ish), but you have to design the board layout well, this translates as 20/10e6 (0.002%) which gives an error over a day of 86400 * 0.002% = 1.73 seconds per day so in a month it looses 30x1.72 = 51 seconds or 1 minute a month (approx).

The modern pic chips have 1% clocks, this is why I use the $8 clock device on the Aeon. So you see 1/3rd of a second per month is fairly accurate as clocks goes.

RJ

Sent from my charge on tapatalk