Drifting seasons

The idea

In a lunar calendar the seasons fall in different months in successive years, because the lunar year is 354 days long while the seasons repeat in about 365 days.

Same month, other season

In a lunar calendar a certain month falls in summer one year. Some years later it falls in another season.

Why does this happen?

• The lunar year is shorter than the time seasons take to repeat
• The Moon changes the seasons
• The months get longer

Compare the years

Press Next step.

Seasons slide

In a lunar calendar, the seasons do not remain in the same lunar months in successive years. This is because the seasons repeat in about 365 days while the lunar year is only 354 days long.

In a lunar calendar the seasons shift to different months from year to year, because the lunar year (354 days) is shorter than the seasons' cycle (about 365 days).

Notes

A lunar year (354 days) is shorter than the seasons' cycle (~365 days), so seasons drift.

Check yourself

How many days long is a lunar year?

Answer: 354 days

A lunar year is 354 days long.

Seasons repeat in approximately …

In a lunar calendar the seasons fall in different months in successive years because …

Which cycle is shorter?

• 354 days. That is the length of a lunar year.
• 29.5 days. That is one lunar month.
• 365 days — correct. Yes!
• the lunar year is shorter than the cycle of seasons — correct. Yes!
• the Moon stops. The lunar year is shorter than the cycle of seasons.
• the months have no names. It is because of the 354-day lunar year.
• The cycle of seasons. The cycle of seasons is about 365 days.
• The lunar year — correct. Yes!
• Both are equal. The lunar year is 354 days, the seasons take about 365 days.