How is the Qingming date calculated?

This is not a real festival,

But one of the 24 solar terms,

After the vernal equinox

Specific calculation method,

As a traditional solar term in China, Tomb-Sweeping Day,

According to the annual vernal equinox,

The vernal equinox will have a solar term every 15 days.

So Qingming is between April 4th and 6th in the solar calendar.

Mostly on the 5th.

Not fixed on April 5 of the solar calendar,

It's not decided by the lunar calendar.

The vernal equinox changes with the rotation of the earth.

The earth's daily rotation is not 24 hours,

But 23 hours and 56 minutes,

One day less every four years.

Thus affecting the time of solar terms,

According to this rule,

Tomb-Sweeping Day in 2008 and 2009 both happened on April 4th.

On April 4th, Tomb-Sweeping Day appeared in 2004 and 2000.

On April 6th, Tomb-Sweeping Day appeared in earlier years such as 1939 and 1935.