People had to try for thousands of years before they knew how to put together days, weeks, months, and years.
This sentence is a passage from an article about "Inventing calendar". The phrasal verb I am so confused is "put together". Does this sentence mean that "they try to create days by combining hours, weeks by combining days, months by combining weeks" or "they try to form a calendar by joining days, weeks, months, and year together"?
Put together (phrasal verb) according to the Oxford dictionary you can put together some parts of something to make a ready-to-use product (e.g. assemble some parts of furniture to make a table or some different articles was assembled and collated in order to make one story)
has idiomatic meaning (e.g. put yourself together) - you can't assemble yourself, it means put together your thoughts
also it has slightly different meaning as (assembled, combined; (occasionally) makeshift, improvised)
your sentence:
People had to try for thousands of years before they knew how to put together days, weeks, months, and years
means to make the right order for days when the only one month should have 28 days and one time out of four years it turns 29 days month so-called 'leap-year'; Consequently, year becomes the entity that has some exact order for days it could be changed due to order
