Because the CZC1 and CZC3 Zone Controllers are not only thermostats but also heating programmers we have included an accurate quartz clock in then to ensure minimal clock drift.
During production we calibrate the quartz crystal on every CZC1 and CZC3 against an accurate clock source to ensure that individual variations between crystals are compensated for. This process means that we do not need to use high cost crystals to obtain accurate time.
The CZC3 has the additional advantage of Automatic Time Set (ATS). When you insert the batteries, the CZC3 automatically sets its clock. It also re-synchronises periodically so that it stays accurate and is updated automatically after the clocks change in spring and autumn.
It does this by receiving the MSF signal transmitted from Anthorn Radio Station in Cumbria (previously located in Rugby).
Not only does this eliminate the need to check the clock, it means you can use the CZC3 as an accurate time reference.