Calculate Time in Century

A calculator for the time lived in the 20th and 21st centuries, or for a period spanning the turn of the century. Sometimes it is interesting to know how far start and end are apart from the turn of the century, if they span across it. The last turn of the century, which was also a turn of a millennium, was the one from the 20th to the 21st century more than 24 years ago. This occurred exactly between December 31, 2000 and January 1, 2001. The year 2000 was therefore still in the 20th century; we have only been in the 21st since the beginning of 2001.
Please enter a start date from the 20th century, this can be a date of birth or anything else. January 1, 1990 is the default. The current date is selected as the end date, this can also be changed, but it has to be in the 21. century. It will be calculated how many days each date is in the 20th or 21st century. For the start date, which lies in the 20th century, the time between this date and the end of the century is calculated. For the end date, which lies in the 21st century, the time between the beginning of the century and the date is calculated. This span is given in days as span 1 and span 2. Both time spans are compared in absolute terms and as a percentage. The first and last day of the total time span are counted in this calculation.

Example: someone was born on November 3, 1996. The creation date of this calculator is October 26, 2025. At that point, this person has lived 1520 days in the 20th century and 9065 days in the 21st century, for a lifespan of 10585 days. Of these, 14.4 percent occurred in the 20th century.