The 20th is the ovulation period

However, we can use some methods to understand the issue of ovulation on the 20th. First, we can check the calendar. During this period, the calendar will usually show a line of numbers called the "ovulation period." For example, if the number on the calendar is 15, then the period is the 15th of the month.

Additionally, we can use some testing tools to understand this period. For example, a thermometer can be used to measure basal body temperature. During this period, a woman's body temperature usually rises by 0.3 to 0.5 degrees Celsius.

While these methods can help us understand this period, they have some limitations. For example, dates on a calendar can be affected by various factors, such as holidays and weather. Additionally, testing tools may not be accurate enough.