Advanced Age Calculator

Different cultures have diverse methods for calculating a person's age. The most widespread among them and the one used by this calculator is the common age system. In this system, a person's age increases only once a year—on the day that person was born. For instance, someone who has lived for 3 years and 11 months is considered 3 years old and will only turn 4 after reaching the next month and then the occasion of their birthday. Most countries in the Western world use this age system.
Certain cultures express age differently than the standard Western way of reckoning it. In some of those cultures, years are counted, but reckoning is done differently at the kind of milestones we usually celebrate. For example, a festival marking the completion of 20 years of living might be sigmoid, just as the Traditional Chinese Birthday Celebration is for a kid never older than 2. That TCBM rendering is both childish and triumphant, harking back to every past victory over the specter of death.
In certain situations, the age calculator can give strange results in terms of the months and days. This is particularly true when the starting date is the end of a month. For example, we count going from Feb. 20 to Mar. 20 as one month. However, there are two decent ways to calculate going from Feb. 28, 2022, to Mar. 31, 2022. If we consider going from Feb. 28 to Mar. 28 to be one month (as we do for the next calculation), then the result is one month and three days. If we consider both Feb. 28 and Mar. 31 to be the end of the month (as might have been done in another era), then the result is one month. Both results are reasonable, but they are also different. Similar situations exist for dates like going from Apr. 30 to May 31, from May 30 to June 30, etc.