CST to CET

Enter a time in US Central Time and read it in Central European Time. CET is usually 7 hours ahead of CST.

Whether the gap holds all year

The gap is not the same all year: it ranges from 6 hours ahead to 7 hours ahead, because US Central Time and Central European Time change their clocks on different dates. Those few weeks are when most calls are missed by an hour.

Which zones these letters mean

CST here means US Central Time. It can also mean China Standard Time, which is fourteen hours ahead of US Central rather than behind it — by far the most costly abbreviation clash in scheduling.

Questions

What does CST actually mean?

It depends who wrote it, and that is the problem. CST is US Central Time and it is also China Standard Time — fourteen hours apart. IST is India, Ireland and Israel. Every conversion page here names the zone it resolved an abbreviation to, rather than quietly picking one.

Why does the difference between two time zones change during the year?

Because countries change their clocks on different dates. The United States moves in March and November, the European Union in the last weekends of March and October, and the southern hemisphere moves the opposite way entirely. For a few weeks each year the usual gap is an hour out, which is when most mis-scheduled calls happen.