With these "truths", producers hope to correct common mistakes and debunk spurious homespun remedies. For instance, it explains that "bananas will aggravate constipation rather than alleviate it" and that "rubbing ginger on your scalp will not make hair grow".

The 2019 edition has already sold over 150,000 copies.

Another major player in the market is the Plants and Animals Calendar created by Guokr, a company that popularizes science among youth in interesting and different ways.

It has been making calendars for the past five years with such themes as "species in Chinese cities that are usually overlooked" in 2015, "species on our table" in 2016 and "species in cities around the world" in 2019.

More than 820,000 copies of the Palace Museum Calendar 2019 have been sold. Owspace Desk Calendar 2019 sold more than 110,000 copies by November.

"The return of calendars' popularity shows that, as people's lives improve, they want quality products that are beautiful and useful," says Wang Guanliang.