See also the
Dr. Math FAQ:
calendar & days
of the week
3D and higher
Browse Middle School Calendars/Dates/Time
Stars indicate particularly interesting answers or
good places to begin browsing.
Selected answers to common questions:
A million/billion seconds.
- The Math of Time [05/15/1997]
What is the connection between math and time?
- Midnight on Which Day? [04/12/2003]
I assumed midnight on Sunday meant Sunday at 12:00 AM. So three and
half days later would be Wednesday at 12:00 PM or noon...but I was
told it was Thursday at noon...
- Military and Nautical Time [06/26/2000]
How do you convert nautical (military) time to standard time?
- Military Time, Decimal Time [08/05/2003]
Filling out time cards for work.
- Military Time, Spoken [10/18/2002]
I need to know the correct way of saying the 24-hour clock system.
- Nanoseconds in a Year [8/29/1996]
How many nanoseconds are there in one year?
- Number of Days between Two Dates [09/06/2004]
Given two dates, how can I mathematically find out the number of days
- Number of Days in a Month [10/21/2000]
Why can't all months of the year have the same number of days?
- Numbers: Cardinal, Ordinal, Nominal? [10/25/1999]
Which group of numbers - cardinal, ordinal or nominal - does "time" fit
into? Are there other types of numbers as well?
- Operations on Measurement Units [08/21/1998]
Why can we divide distance by time, but not add distance to time?
- The Origin of Month Names [10/17/1998]
If oct is the prefix for 8 and dec is the prefix for 10, why is October
the 10th month and December the 12th month?
- Perpetual Calendar [10/21/1998]
How do you figure the perpetual calendar?
- Seconds in 1000 Years [02/13/2002]
I need to know how many seconds are in one thousand years, including leap
- Seconds since 1980 [08/08/2002]
How can I work out the number of seconds since 1980, taking leap years
- Subtracting Military Times [05/21/2000]
How can you calculate the duration of a phone call (in minutes) if you
are given a start and end times in military time?
- Subtracting Time [02/27/2001]
A marathon runner crossed the finish line after running for 2 hours, 48
minutes, and 12 seconds. She crossed the line at 9:18:12 A.M. When did
the marathon start?
- Telling Time: A.M. and P.M. [10/30/2001]
What do A.M. and P.M. mean?
- Time Zones [05/09/2003]
How do time zones work?
- Watch Gaining Time [11/10/2002]
A watch is set accurately at midnight, but gains six minutes every
hour. If it stopped 30 minutes ago, and now snows 8:26 a.m., what's
the correct time now?
- What Day of the Week was 4/13/96? [07/12/2002]
What day of the week was April 13, 1996? I know the answer is
Saturday but I have no idea how to figure it out.
- What Day of the Week Was a Given Date? [01/05/2006]
Is there a simple way to figure out what day of the week any date in
history fell on?
- What Time Did Ajay Start? [08/06/2003]
Three persons, Ajay, Bhanu, and Chandu, plan to travel from P and reach
Q at 4.00 PM...
- When Does Your Birthday Fall on the Day You Were Born? [02/20/2004]
I'm curious how many years pass before your birthday falls on the day
of the week you were born?
- When Were They Born? [04/30/2002]
Two people celebrate their birthdays on the same day this June. One
of them is exactly 2555 days older than other. In what years were
- Why Does 1 Degree Equal 60 Minutes? [07/28/2004]
In 60 minutes, the minute hand of a clock makes a full circle, which
is 360 degrees. How can 60 minutes equal 1 degree when measuring angles?
- Will Zeller's Rule Work Indefinitely? [04/07/2004]
I showed an equation involving Zeller's Rule to a college teacher and
he told me the equation may not work for very distant years, because
the exact value relating the day of the week to the year, month, or
date may involve irrational numbers. Is that correct?
- World Time Zones [10/24/2001]
What time is 20:00 in the UK, when converted to Central time in the USA?
- Writing Hours and Minutes in Decimal Form [11/05/2004]
How can I convert 6 hours and 7 minutes into a decimal form of hours
for my timesheet? How does the 7 minutes become a decimal?
- Year 2000 [07/13/1999]
Is the year 2000 a leap year?
- Years That Start on Sunday [10/02/2000]
What is the probability that a randomly chosen year will start on a