Mark 13:28-30 (ESV)
"From the fig tree learn its lesson: as soon as its branch becomes tender and puts out its leaves, you know that summer is near.  So also, when you see these things taking place, you know that he is near, at the very gates.  Truly, I say to you, this generation will not pass away until all these things take place.
“Truly I say to you, this generation will not pass away until all these things take place.” Yes Jesus spoke of things yet to come, but they have all happened within the days of the Apostles. In large part that is the meaning of Peter quoting Joel in the second chapter of Acts. They have all happened. The fig tree has put out its leaves. The end is near. Jesus tells us no one knows the day or the hour. No one does. We live every day knowing he could come back at any time. We wait for it in a mixture of joyful expectation, and fear. For us it will be a joyful homecoming. But not for everyone. So why we wait, and with joyful expectation hope for a speedy return, we work knowing the days grow shorter and soon will be the end when the day of calamity strikes, when it will be too late for others to seek him any longer.