is a period cycle 21 to 35 days for all ages?

Hi,
Welcome to ehealthforum,
The normal menstrual cycle duration remains the same for women in reproductive age group. Variation of 5-10 days in menstrual cycle length is considered to be normal (as long as you have regular periods). If you are having irregular cycles or long gap between periods, chances are that you are having anovulatory cycles (menstrual cycles without periodic egg release from ovary). It is important to look for and treat the underlying cause for the irregularity of periods. Visit your doctor/gynecologist for further evaluation to look for the underlying cause. Treatment as appropriate (based on examination findings and investigations results) would be started to help you regulate your periods. Be in regular monitoring and follow-up with your treating doctor/gynecologist and report any new/abnormal symptoms immediately.
Take care.