Yes, your landlord absolutely has to tell you when he is planning on entering your apartment! With the exception of an emergency situation (flood, fire, etc), any current Landlord Tenant Act will state that the landlord must give tenant at least 24 hours notice before he plans on entering the apartment.
Hope this helps!

Yes the landlord has to notify you of his entering the unit. Check your lease, as it should give the specifics. Most require a 24 hour notice.

Your landlord has no right to be in your home without proper notice and if you catch them there you can actually have them forcibly removed by the police. Yes, this is the one way you can actually get traspassing or breaking and entering charges pressed against you for entering your own property as you well please, if you are renting it out. By law if you are renting you have the same legal rights as if you owned the property in this situation. wow!

Typically, your LL's rights to enter your leased premises are defined in the Lease (and, by the way, even if your Lease has expired, and you're month-to-month, the written terms of the Lease still apply as the best written evidence of what those terms are). Generally, the LL can enter to insure the safety of the property or adjoining property, to "arrest a nuisance" ( = stop a problem, not lead someone away in chains), to work on the property (generally with notice), etc. They can't just come in and 'poke around' - you pay for your space and it's your space and you have what's known in 'common law' as the "right to quiet (uninterrupted) enjoyment". This all goes to hell 1 or 2 months before the lease expires when the LL can show the property for sale or rent at 'reasonable' times and hours and have "Open Houses" with reasonable notice which can't be 'unreasonably' withheld by the tenant. Lots of "reasonables" but that is a legal standard applied throughout our legal framework.