"Until" is the correct word. " Till " or sometimes " 'til " mean the same thing, and are informal abbreviations of the word "until" . They're fine in conversation or informal writing, but you shouldn't use them in formal English. In the example above, yes, you could say 'to'. It doesn't always mean the same as 'until', but here it does.

Nine days until summer.. I work from 7 am until 5pm.. More samples [M] [T] We talked until two. [M] [T] I'll stay here until ten. [M] [T] Wait until further notice. [M] [T] Wait until tomorrow morning. [M] [T] I waited until the last minute. [M] [T] Do you plan to work until 10:00? [M] [T] Are you going to work until 10:00? [M] [T] She ignored him until he became rich. [M] [T] Class doesn't begin until eight-thirty. [M] [T] I'll be waiting for Tom until 6 o'clock. [M] [T] Do you plan to continue working until 10:00? [M] [T] Are you going to continue working until 10:00? [M] [T] I didn't know about it until I read the paper. [M] [T] I didn't know about that until quite recently. [M] [T] Let's leave things as they are until he comes back. [M] [T] He practices playing the guitar until late at night. [M] [T] There was nothing to do but wait until the next morning. [M] [T] I promise you I'll stay with you until your father arrives. [M] [T] He doesn't like to wait until the last moment to do something. [M] [T] My mother asked me not to feed the dog until after we had all eaten. [M] [T] I knew I shouldn't have put off doing my homework until the last minute. [M] [T] A lot of people who have up until now been spending money having a good time now need to be more careful with their money.