A-V Valves Open; Semilunar Valves Closed. This is the first phase of the cardiac cycle. It is initiated by the P wave of the electrocardiogram (ECG), which represents electrical depolarization of the atria. Atrial depolarization initiates contraction of the atrial musculature.
Community Q&A. You can calculate age on Excel for a many applications by combining an undocumented function and the date format for cells. Microsoft Excel internally stores dates as serial numbers, which is the number of days a date is from Jan. 1, 1900.
Method B: Convert birthdate to age with DATEDIF function. Some would like to apply the DATEDIF function to calculate the age. Enter the formula =DATEDIF(A2,NOW(),y) in a blank cell, it calculates the age immediately after pressing the Enter key. Method C: Convert birthdate to age with ROUNDDOWN function.