With examples from Babylon 5.
According to a variety of sources, including Dictionary.com, till is not actually a derivative of until at all. In fact, till and until can be used interchangeably, while 'til is actually considered a spelling error, despite its common usage in the advertising industry and old poetry.
Susan stared at the clock and repeatedly muttered, "I will stay 'til my shift is over before I go kill Garibaldi."
Susan glared back at Elizabeth Lochley. "You will not dock your ship, Commander, till I say it's time for you to do so. Babylon 5 out."
Most style guides will stress using until in the written form, barring specific instances of phrasing, like the examples below.
Interestingly enough, according to this article over at Motivated Grammar, the word till may actually be older than until. This means that until is a derivative of till, and 'til is still an incorrectly spelled derivative of until. Bearing this in mind, it's a matter of your location as to which you use in place of until. The examples listed in this article show that till is more commonly used in Scotland, while the incorrect 'til is more commonly used in the United States.
Within this article over at English Language & Usage, there's a discussion in the comments about the differences in using till (continuous actions) and until (perfective), but it still states that 'til is incorrect and should be avoided.
What this all boils down to is that you should use till instead of 'til in place of until, unless you're using very specific phrases that already are known to use 'til, like the examples given above.
- til @ Dictionary.com
- until @ Dictionary.com
- Until, Till and 'Til @ World Wide Words
- il v. till v. ’til v. until @ Motivated Grammar
- What is the difference between “till” and “until”? @ English Language & Usage
- Till and Until Are Different
- Non-Errors @ Common Errors in English Usage