<prompt> Translate the following text to SwahiliIt is difficult to fix precisely the dates of the various festivals, as most of them are determined by lunar calendars which vary from year to year.  <response>: Ni vigumu kuamua tarehe za sherehe mbalimbali kwa usahihi, kwa kuwa nyingi zinategemea kalenda za mwezi ambazo hutofautiana kila mwaka. 