http://www.chabad.org/library/moshiach/article_cdo/aid/101680/jewish/Date-of-Mashiachs-Coming.htm
Date of Mashiach’s Coming
The actual date of the Messianic redemption is a guarded mystery unknown to man. It will happen “in its time” (Isaiah 60:22), predetermined from the beginning of creation. This ultimate ketz (time for the ‘end’) is unconditional: it does not depend on Israel’s merit, as it is said, “For My own sake, for My own sake, I will do it…” (Isaiah 48:11); “I wrought for My Name’s sake that it should not be profaned in the eyes of the nations.” (Ezekiel 20:9)
Even so, the wording of Isaiah 60:22 seems to display a contradiction by stating “in its time I will hasten it”: “in its time” means a set date; “I will hasten it” means that it may occur earlier, before “its time.” The contradiction is resolved as follows: “If they are worthy ‘I will hasten it;’ if not ‘in its time.’ ”
The implication is clear: Mashiach can come any day, even before the predetermined date: “This day if you will listen to His voice!” (Psalms 95:7) Every generation has a special ketz of its own, for, as stated, Mashiach is alive and present in every generation, albeit concealed. He is ready to be revealed at a moment’s notice. In the course of history prior to “its time” there are especially auspicious times when it is easier to effect his coming. To take advantage of these, to hasten the redemption, that depends completely on us.
You said:
“If they are worthy ‘I will hasten it;’ if not ‘in its time.’ ”
Can you elaborate? What makes one worthy to hasten that time?