In my previous post I explained how to interpret times in Dutch acts. Those times were usually local times. That sounds obvious, but local time was really local - every place could have its own time.
In the 18th century, time calculation was usually based on the sun - noon is when the sun is at its peak. With this system, there is a one minute time difference when you travel 17 km (10.5 miles) east or west.
There were some changes in the time calculation after the 1830s (like the introduction of mean time), but every town kept its own time throughout the 19th century. To make matters worse, the railway companies introduced their own time, as they could not handle the different times at each station very well. Towns and cities with a railway station now had two times: local time and railway time. Railway time was equal to Amsterdam mean time (AMT).
Time zones, based on Greenwich mean time (GMT) were introduced in the U.S.A. in 1884, and in Europe in 1892. Neighbouring countries Belgium and England used GMT, Germany used central European time (CET, with a one hour offset to GMT), and in The Netherlands a discussion on the introduction of time zones started. In the mean time, the railway time changed to GMT, some towns followed the railway time, some towns used AMT, some towns used local time, and in most places at least two times were in use.
The discussions and confusion finally ended in 1909, when AMT became the official national time.
Amsterdam mean time was 19 minutes and 32 seconds ahead of Greenwich mean time. In 1937, the time was adjusted by 28 seconds to achieve a twenty minute offset to GMT.
CET was enforced by Germany in 1940, during the German occupation of The Netherlands in the second world war. It is still in use today.