Good morning sir/mam Why my period going late date...

Treatment for Delayed period
first of all the normal cycle between 22-32 day so if your menstural cycle between this time ypur period is normal and you donnt need any medication and you must go away of stress and eat good nutrition and do routeinly soprt but if your period more than normal you can take duphaston tab two pills daily for 10 days, with psychological and mental comfort and avoiding stress and anxiety, and regular eating healthy, rich in vitamins and essential elements for the body, with a lot of drinking water daily, treatment of chronic diseases such as thyroid problems ,and Pelvic inflammatory diseases
What are the required investigations and tests 
Clinical assessment and Urine pregnancy test if your period was delayed .and Blood Hcg level  in addition US Abdomen .
 and must do FSH , LH . TSH , T3 and T4
What are the causes of menstrual cycle delay 
Pregnancy
Stress amd Anxiety
Hormonal disturbance
PCO polycystic ovary
Thyroid dysfunction
Pelvic inflammatory diseases
Hypothyroidism
High prolactine
my advise
Regularly take the previous treatment, see a doctor if the menstruation continues to be delayed