Checking the server time changes due to the summer time changeover - script for MetaTrader 5

Unfortunately, I had to realise that some brokers are a bit careless with the
server time changeover, which I had not expected
and which surprised me very much.

The FOREX session lasts exactly 120 hours:
from Sunday 17:00 Eastern Standard Time (North America) or EST
to Friday 17:00 EST.

The problem arises from the time changes to summer time and winter time,
which do not take place on the same Sundays in the different regions of the world.

For example, the USA changes on the 2nd Sunday in March and the 1st Sunday in November,
which also affects the start and end of the FOREX session.

The EU changes on the last Sunday in March, i.e. after the USA, and on
the last Sunday in October, i.e. before the USA (see timeline above).

This creates a transition period in which the US and the EU have a different
time difference than the normal differences of 5
hours (London), 6 hours (Frankfurt, CET) or 7 hours (Cyprus, EET).

In this interim period, this change in time difference should be reflected in the
changed timestamps of the first and last hour of the FOREX session.
So if the FOREX session starts on Monday at 00:00 (EET, MQ time), it should
start one hour earlier after the change in the US, i.e. at 23:00 on Sunday,
and end one hour earlier on Friday, i.e. at 23:00 (or 22:59:59).

But unfortunately I had to realise (and with this script anyone can check this with their
broker) that on an MQ demo account and on accounts of some real brokers
the first hour always(!) appears on Monday at 00:00, but the last hour appears as expected
on Friday at 23:00 (or 22:59) or one hour earlier. This means that the first hour
of the FOREX session, in which the trader or an EA could react to events at the weekend, is missing.
The end of the FOREX session can also no longer be determined by simply adding120 to the
first hour of the FOREX session, e.g. to close all positions before the weekend.

This script now checks the broker's time changes in the past and logs all
FOREX sessions that are obviously incorrect (odd) or not 120 hours. If there are 120 hours between
the first and last hour of a FOREX session, there is no printout in the log.

At the end, the script prints the last retrieved timestamp, the number of
shortened sessions found and the approximate number of years checked.