A single week is the first week of school, the third week is odd weeks, the second week is biweekly, and the fourth week is even weeks.

The second week of formal class means that the first week is administrative week, which is used for other purposes.

Some courses are taught alternately once a week and twice a week. One class this week and the next next next week. There is plenty of time and credit line, neither more nor less.

Extended data:

In different regions, the start time of a week is not exactly the same. In many English-speaking countries, Judaism and Japan, today is Sunday, and Egypt Week begins on Saturday. Most European countries regard Monday as the first day of the week. Chinese mainland once thought that Monday was the time to start.

But more and more English dictionaries begin to define Monday as the first day of the week, otherwise the word weekend will be difficult to make sense.

From a religious point of view, the Bible believes that God created everything in the world in six days, and rested on the seventh day. The seventh day began on Sunday, and the seventh day was Saturday, so Judaism took Saturday as the Sabbath.

After Christianity became the state religion of ancient Rome, because Jesus was resurrected on Sunday, Sunday was changed to Sunday; Islam believes that God completed his creation on the sixth day, which should be celebrated, so Friday is designated as the main day of worship.