A Tongshu (通書) is a traditional Chinese almanac. It combines calendar information with systems used to describe the character of a day and its suitability for different activities.
More than fortunate and unfortunate
Almanac entries may include the sexagenary day, lunar date, solar terms, daily officers, directional cautions, and lists of activities traditionally considered supported or discouraged. Different editions and lineages do not always calculate or prioritize these signals in the same way.
Context changes the question
A day described as supportive for one activity may be neutral for another. Personal timing methods can add another layer, and practical constraints still matter. Date selection works best as a structured comparison, not a guarantee.
Use the almanac transparently
Purple Heaven’s Tongshu experience aims to show why a date receives a label. Visible factors, plain-language explanations, and calendar assumptions make the recommendation easier to examine rather than simply obey.