Hi & Welcome. If you wish to prepone a period, treatment should be initiated as early as the first week of the cycle. At least a week of medication is necessary to create the hormonal situation necessary to induce an early period. Moreover, if you wish to prepone the period you can t predict withdrawal bleeding within the expected time. It may be delayed or occurs earlier which can mess up your wedding celebrations and it may make the next cycles irregular. Hence I would advise you to postpone your period. To postpone your period you need to take one tablet of Norethisterone 5 mg (PRIMOLUT-N) 2 times a day, beginning 3 days before you expect your period to start i.e., you may start taking the tablet from 21st December on wards. You should take the tablets at the same time every day, one in the morning & in the evening. Continue it as long as you wish (maximum up to 2 weeks). Then stop the medicine. Withdrawal bleeding will occur within 3-7 days. Remember you might get some side effects like nausea, vomiting, abdominal cramp, irregular spotting, breast tenderness may develop in next cycle if you continue the pill for long time. Since this is a prescription based medication so you need to take it from your doctor. Hope this answers your query.