Hi my wife took primolut N to delay her period...

will the next period come in the original date or new date according to the delayed period ?
thats not for sure , but usually the female should start counting according to the lastest period wheather its the new date or original date , so counting should start from new delayed period date 
How to know ovulation days and the safe days in period :
1. ovulation time or the time ovum exist are the first 4 days of the last 16 days of the period , for example ;if your period is 28 days , and  if your first day of period was 1st/9 , your ovulation time is 12th-16th /9 
2. the ovum last 48 hours in the uterus and can get fertilized any time during this period of time 
3. male semen lasts up to 5 days in female uterus and will be able to fertilize during this period of time , but the earlier the better 
normal length of period :
21 - 40 days 
normal length of period bleeding :
2 - 7 days , and usually its around 4 - 6 days