Generally, chaar din ki zindagi, literally four days of life, is used in context for small life, a life that will pass soon. But in haule-haule of Rab ne bana di jodi, Jaideep Sahni uses it in almost an opposite meaning, where he says 'tu sabr to kar mere yaar... hain din jindadi de chaar' (be patient, the life is four days long) which almost reverts the meaning of the phrase if it has to keep things in sync and the sentences meaningful.
Thanks to the wonderful singing of Sukhwinder, nobody had time to wonder about the words in that depth.