I live in Toronto, Ontario in Apartment building. I gave a notice before 60 days to vacate my unit but by mistake wrote July 25 instead of July 15. Next month when it came to my notice I informed in writing to change the date July 15. Property Manager informed me that he will charge a full month rent even though I leave earlier in half way of the month.
My tenancy agreement states as below: Any monthly tenancy may terminated by giving notice not less than 60 days before the date the termination is specified to be efficetive and shall be specified to be effctive on the last day of a month of the tenancy.
Can I eligibel to charge only half month of rent as I am leaving on 15th of the month?
Thank you for your time.

It sounds like your rent is final on the last day of the month in which your notice states.

So by what you posted, yes you would owe the full month.