As Christians we know that Jesus will come back again, and whilst we want to know when, so did the disciples! Tom and Dean look at the next small passage in Mark where Jesus tells them to be ready.
Mark 13:28 - 13:31
28 “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. 29 So also, when you see these things taking place, you know that he is near, at the very gates. 30 Truly, I say to you, this generation will not pass away until all these things take place. 31 Heaven and earth will pass away, but my words will not pass away.