Date & Age Calculator Guides

Explore keyword-rich tutorials for every calculator on DateCalculatorOnline.com. Each guide below answers common search questions, shows when to use a tool, and links directly to the calculator so you can get answers fast.

Tip: Bookmark this hub—search engines love internal links and structured content, and you get one-click access to every tool.

Project and planning calculators

Date Difference Calculator – Calculate days, weeks, months, and years between two dates. Popular searches: “how many days until my deadline?”, “days between two dates calculator”.

  • Enter start and end dates to see total days and breakdowns.
  • Use the working-days variant below to remove weekends and holidays.

Working Days Calculator – Count business days while skipping weekends and custom holidays. Popular searches: “add business days to a date”, “workdays between dates”.

  • Input start/end dates and optional holidays for accurate office timelines.
  • Great for delivery promises, compliance timelines, and sprint planning.

Add or Subtract Date Calculator – Add days, weeks, months, or years to a start date. Popular searches: “what date is 90 days from today?”.

  • Select the time unit and value to jump forward or backward.
  • Ideal for setting reminders, reviewing contracts, or planning travel.

Time Duration Calculator – Measure hours and minutes between two date-time points. Popular searches: “calculate hours between two timestamps”.

  • Add start and end date-time to see total duration.
  • Useful for support SLAs, shift planning, and event timing.

Age, birthday, and anniversary tools

Age Calculator – Exact age in years, months, and days. Popular searches: “how old am I in months?”, “age in days calculator”.

  • Enter your birth date to see age and total days lived.
  • Includes days until next birthday for quick celebration planning.

Age on a Specific Date – Find your age on any future or past date. Popular searches: “how old will I be on…?”.

  • Set a target date to check milestone ages and eligibility dates.

Next Birthday Calculator – See the weekday and countdown for your next birthday.

  • Great for party planning, time-off requests, and social posts.

Birthday Calculator – Discover the weekday you were born, days since birth, and milestones like 10,000 days.

Age Difference Calculator – Compare two birthdays to see who is older and by how much.

Anniversary Calculator – Track relationship or event length with countdowns to the next anniversary.

Health, fertility, and family planning

Period Calculator – Estimate upcoming periods, ovulation, and fertile windows. Popular searches: “next period date calculator”, “ovulation window calculator”.

  • Enter your last period start date and average cycle length.
  • Use results to plan trips, workouts, and health appointments.

Chinese Gender Predictor – Folklore-based boy/girl guess using birth date and conception date.

  • Fun-only tool; not medical advice. Shows lunar age and conception month used.

Quick lookup utilities

Day of Week Finder – Find the weekday for any date.

Day Number of Year – See which day of the year a date is and how many days remain.

Week Number Calculator – Get the ISO week number and year for any date.

Days Until Calculator – Count down to events, deadlines, and holidays.

FAQs from searchers

What is the fastest way to count days between two dates?

Open the date difference calculator, enter your start and end dates, and you will see total days, weeks, months, and years instantly.

How do I add business days to a deadline?

Use the working days calculator and include your holiday list. It removes weekends automatically so your schedule stays realistic.

Can I check my age on a specific date for visa or eligibility?

Yes. The age on date calculator lets you pick any date to confirm age-based cutoffs for visas, contests, or benefits.

How many days until my due date?

Enter your due date in the days until calculator to get an exact countdown. Pair it with the period calculator for cycle-based planning.

Is the Chinese gender predictor accurate?

It is a folklore tool with a 50-50 chance. Use it for fun only. For medical accuracy, rely on your healthcare provider.

Why searchers choose DateCalculatorOnline.com