Important Days Calculator

To calculate a date in the future:

1. Enter your starting date in the "Start Date" field
2. Select "Add Days" from the calculation dropdown menu
3. Enter the number of days you want to add in the input field
4. Click the "CALCULATE" button

The calculator will show you what date falls exactly that many days in the future. This is useful for deadline calculations, project planning, or determining dates for legal documents.

To find the date of an anniversary:

1. Enter the original date of the event in the "Start Date" field
2. Select "Find Anniversary" from the calculation dropdown
3. Choose the anniversary year you want to calculate (e.g., 10th, 25th, 50th)
4. Click the "CALCULATE" button

The calculator will show you the exact date of that anniversary. This feature is perfect for planning wedding anniversary celebrations, work milestones, or commemorating important events.

To find the date of the next upcoming holiday:

1. Enter your reference date in the "Start Date" field (usually today's date)
2. Select "Next Holiday" from the calculation dropdown
3. Choose the specific holiday you're interested in from the holiday dropdown menu
4. Click the "CALCULATE" button

The calculator will determine when that holiday next occurs after your reference date. This helps with vacation planning, scheduling events, or just knowing how many days until a particular holiday.

Note that some holidays (like Easter, Mother's Day, and Thanksgiving) have dates that change each year. The calculator accounts for these variations automatically.

To calculate a date in the past:

1. Enter your reference date in the "Start Date" field
2. Select "Subtract Days" from the calculation dropdown
3. Enter the number of days you want to subtract in the input field
4. Click the "CALCULATE" button

The calculator will show you what date falls exactly that many days in the past. This can be useful for historical research, determining origins of projects, or calculating retroactive dates.

The "Week number" in the results section refers to the ISO week number for the calculated date. This is a standardized way of identifying weeks throughout the year, where:

• Week 1 is the first week of the year that contains a Thursday
• Each week starts on Monday and ends on Sunday
• A complete year has either 52 or 53 weeks

Week numbers are often used in business planning, project management, and production schedules. They provide a consistent way to refer to particular weeks across different years.

Holidays are calculated using two different methods, depending on their nature:

1. Fixed-date holidays: Holidays like New Year's Day (January 1), Valentine's Day (February 14), and Christmas (December 25) occur on the same calendar date each year.
2. Variable-date holidays: Holidays like Easter, Mother's Day, Father's Day, and Thanksgiving have dates that change from year to year according to specific rules:

• Easter: Calculated based on ecclesiastical rules involving the first Sunday after the first full moon following the spring equinox
• Mother's Day: Second Sunday in May (in most countries)
• Father's Day: Third Sunday in June (in most countries)
• Thanksgiving (US): Fourth Thursday in November

When you select "Next Holiday," the calculator determines the next occurrence of that holiday after your specified start date, even if it falls in a subsequent year.