Responsive Calendar

I work with dates a lot and have written both a monthly  calendar and weekly schedule that clients update through a database interface.

Programming languages like PHP have fantastic support for working with dates and times. As you don't seem to be a programmer, you will probably use an off-the-shelf solution. Just the same, here are some tips, (assuming a LAMP environment):

• Store dates using the MySQL format as datetime objects. (YYYY-MM-DD HH:MM:SS). Never store or work with dates as human-friendly text. The human-friendly version can be displayed on a webpage at the end; that's all.
• Pay attention to timezones. You may be in one timezone, your web server may be in another, your ecommerce payment system in another and the database in yet another. I standardize everything to UTC and use PHP to convert to the local timezone on-the-fly when datetimes are displayed.
• Dates are crazy because not all months have the same number of days, not all years have the same number of days (leap years), and datetimes are not strictly base 60 (seven days in a week?). Computer languages have built in algorithms to deal with this craziness. Don't try to do the math yourself. But you have to learn how to work with the language's datetime functions.