Okay, here is a Chinese article with the title "Menstrual Ovulation Period on the 27th":

If your menstrual cycle is 28 days, your ovulation will be around the 10th. However, if your cycle is 30 days, your ovulation will be around the 11th. Also, if your cycle is 40 days, your ovulation will be around the 12th.

No matter how many days into your cycle, you can find out when you are ovulating by taking your temperature. Generally speaking, on the days when your body temperature rises, between 3pm and 5pm each day, your body is starting to produce eggs.

In addition to taking your temperature, you can also find out when you're ovulating by observing your symptoms. For example, if you have very light periods, your ovulation date may be closer to the 10th. Also, if your period is on time, your ovulation date may be closer to the 11th.

keyword: your ovulation own