No set date--even if your landlord put a specific date in the lease agreement it would likely be invalid on grounds of implied warranty and covenant of habitability, provided the landlord has received actual or constructive notice of the violation, and has unreasonably failed under the circumstances to take prompt, effective steps to repair or remedy the condition.
You must notify your landlord in writing. Do that immediately if you have not yet done so.
Then, recommend you immediately contact a local LL-Tenant attorney--frequently a letter from the attorney to the LL is enough to set matters straight. Use the avvo.com search option or contact your local bar association and request a referral.
ME’s LL-Tenant laws can be reviewed at http://www.mainelegislature.org/legis/statutes/14/title14ch709sec0.html
There is also a legal services agency in ME, Pine Tree Legal assistance http://www.ptla.org/
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I can't say what the date is in Maine, but I know in Massachusetts the landlord must turn the heat on by September 15. I would be willing to bet the date in Maine is roughly the same time of the calendar year.
I would recommend you address this concern both in writing and verbally to the landlord immediately. It may also be wise to contact an Attorney licensed in Maine if the problem persists. This is quite obviously a very serious matter that must be addressed immediately.
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