timing period - HEALTHY
Jezebel: The Timing of Your First Period May Be Linked to Cardiovascular Disease Well, this is great. The timing of your first period, while previously linked only to bleeding through your gym shorts on seventh grade dodgeball day, may be an indicator of your risk of adulthood ... The Timing of Your First Period May Be Linked to Cardiovascular Disease Intuitively, "time" would mean simply what time does it start, and "timing" would suggest you want a schedule (what time does it start and end and if it's divided into sections what time do each of them start and end).
Context Explanation
But dictionary definitions don't really support this distinction.