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Ryan, Engineer
Category: Math Homework
Satisfied Customers: 9077
Experience:  B.S. in Civil Engineering
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Quick question about the time...Let's say i was born on jan

Customer Question

Quick question about the time...Let's say i was born on jan 14 1988 @ 11:55am ...
when exactly i'll turn to 28?
does it mean that on jan 14 2016 at 11:55am exactly ill turn 28?
cause as we know time changes!!
Submitted: 1 year ago.
Category: Math Homework
Expert:  Ryan replied 1 year ago.


Thank you for using the site.

The short answer is yes, you would have completed 28 years of life at 11:55 am on January 14, 2016 (Happy birthday, if that is your actual birthdate!).

The longer answer depends on how picky you wish to be about things like leap years, leap seconds, and how one wishes to define one year.

One definition of a "year" is 365 periods of 24 hours. If one wanted to be strict about this, you would have completed 28 full "years" a week prior to January 14th, due to the seven leap years that have occurred between January 14, 1988 and January 14, 2016.

Another definition of a "year" is the time that it takes for the Earth to complete one revolution of the Sun and return to its "starting point" in its orbit. This period is approximately equal to 365.25 days. After four years that additional 0.25 days per year adds up to a full day, which is why we have a Leap Day every four years (with some exceptions).

There are also occasional "leap seconds" added to make small adjustments to the current time.

Thus, the "exact" time depends on how one defines a year, and how one wishes to treat the various adjustments.

From a civil/legal perspective though, you would have been considered to turn 28 at the stroke of midnight between the 13th and the 14th of January, without regard to the exact time of your birth on that day, or any of the various adjustments made to the calendar during those years.

I hope this helps. Please feel free to ask if you have any additional questions about this.



Customer: replied 1 year ago.
Well i need to lnow if i can come upwith an exact time...obviously i dont think the same time and the same day is the right answer due to the leap year , and spiningearth,...there was a moment 28 years ago and i eanna know whrn that moment is in this year!do i make sence
Expert:  Ryan replied 1 year ago.


Well, that's part of the problem. How does one define that "moment"? Is it the passage of a certain number of hours/minutes/seconds? Or is it when the Earth returns to that same position in space? An argument could be made for either definition, so what really matters here is how YOU want to define it.


Customer: replied 1 year ago.
Basically as ure telling me because of leap year and stuff the time cant be the exact time which is 11:55
Im mor3 curious about when earth return to the same positin that it was on 1155 jan 14 1988
Expert:  Ryan replied 1 year ago.

Ok, in that case, we are talking about the "sidereal year", which is the time required for the Earth to return to the same position relative to a fixed frame of reference. The length of that year is 365.25636 days.

28 sidereal years is then 28 * 365.25636 = 10,227.17808 days, or 10,277 days, 4 hours, 16 minutes, and 26 seconds.

Adding this number of days/hours/minutes/seconds to the birth time of 11:55 am on January 14, 1988, the 28th return of the Earth to the same position would be at 4:11 (and 26 seconds) PM on January 14th, 2016.

Note that you do not have to account for leap years in this case, as the leap day added to the calendar during a leap year is intended to help the "regular" calendar "keep up" with this sidereal year. If we didn't add in the leap day, then the seasons would slowly migrate through the calendar months.


Customer: replied 1 year ago.
One last question as u said its the matter of moments.if we go with what u said first which is certainhours minutes and second.whats the answer will be?
Expert:  Ryan replied 1 year ago.

In that case, we would define a year as 365 days of 24 hours each. This is a "civil" definition of a year, and is not exactly related to the movement of the Earth. It is a value that is rounded off for convenience for civil purposes (which is not an uncommon practice in many areas, because perfection is often not worth the effort or expense). Again, this rounding off is the reason why we have leap years. The leap day corrects for the sloppiness in rounding a year off to just 365 days.

28 full years under this definition would be 28 years * 365 days per year = 10220 days.

Adding this number of days to the birthdate of 11:55 am on January 14, 1988 would give 11:55 am January 7, 2016 as the date of the 28th anniversary.


Customer: replied 1 year ago.
U said form a civil prespective illbe28atthe stroke of midnight of 13/14...what do i exaclty mean? 13 midnight? 14 ealry morning? Or 12 midnight;13 early morning??
Expert:  Ryan replied 1 year ago.

What I meant by that is that as far as any legal consideration would be concerned, you would "turn 28" at the moment that the calendar date changed from the 13th to the 14th.

For instance, if the drinking age is 21 years, you would be considered to have attained that age in the first minute of the calendar date of your birth, even if you were actually born very late in the day. So, if you happened to be born just before the stroke of midnight at the end of your birthday, you would be considered to turn 21 at the beginning of the day. You would technically be almost a full day short of actually being "21 years old" in terms of elapsed time, but it would be close enough for civil purposes.

Customer: replied 1 year ago.
Which one you think is more accurate
Expert:  Ryan replied 1 year ago.


I can't really say which one is more "accurate" as there is no agreed-upon standard for what would be considered "correct".

I would tend to think of the sidereal calculation (the one that came up with 4 pm-ish on January 14th) as being more meaningful, since it relates the return of the Earth to the same starting position that it occupied at the time of birth. This is really an arbitrary method of measurement, but at least it's based on something real and measurable.

The civil calculation is rounded off to such a degree that while it may be "correct", I think that most people would balk at the idea that their "28th birthday" falls on a day that is a week before the usual date on the calendar. Socially, we are too accustomed to having our birthday recognized on the same calendar day each year to allow for that.

I hope this helps.

Customer: replied 1 year ago.
Thank you for ur help!!
Expert:  Ryan replied 1 year ago.

You're quite welcome. :)