This is all covered by Civil Code section 1954. It starts out by listing the circumstances in which the landlord may enter, and there are several. Then it limits the time of day for entry except in emergencies or when the tenant has abandoned the premises or when the tenant consents. Next, it says the landlord cannot abuse the privilege of entry to harass the tenant.
It goes on to require reasonable prior notice except in emergencies, and to state that 24 hours' notice is presumed reasonable, meaning unless there are unusual circumstances 24 hours is OK but longer or shorter notice might be required to be reasonable in some cases.
Next, as to the contents of the advance notice, the second sentence of subsection 1954(d)(1) says "The notice shall include the date, approximate time, and purpose of the entry."
There are a few additional provisions in CC 1954 that don't directly pertain to your question, such as how the notice can be delivered, authorizing the landlord and tenant to make other voluntary arrangements, and so on.
So, re-read the three prior answers and form your own opinion as to who is right and who is wrong and who is partly right and so on.