## September 9th time_t errorgreenspun.com : LUSENET : Y2K discussion group : One Thread |

Time_T Discussion

The variable

time_tis a standard data type used to store the number of seconds since the standard UNIX Epoch, 00:00:00 January 1, 1970 UTC. When this variable reaches 10 digits (1,000,000,000 seconds), it can be calculated fairly straightforwardly as follows:

- Every four years there is a leap year between 1900 and 2100 (but not including 1900 or 2100). In effect, only the first rule for leap-years is at work during this span of years since in the year 2000 both the second and third rules apply which means they cancel each other out.

- Starting with every day having 24 hours/day * 60 minutes/hour * 60 seconds/minute = 86,400 seconds/day.
If we divide the

time_tten digit quantity we are interested in (1,000,000,000 seconds) by the number of seconds in a day, we can find out how many days into the UNIX Epochtime_twill hit ten digits. The calculation is as follows:Using the full days (11,574) part gives us years by dividing 11,574 days by 365 days per year:

- 1,000,000,000 seconds / 86,400 seconds/day = 11,574.074074 days

31.709589041 years BUTduring that time interval there would be 8 leap years so the calculation would actually be:(11,574 days minus 8) divided by 365 = 31.687671233yearsSo we now know that it will be 31 years (with 8 of them being leap years).

This accounts for 11,323 days (31 years * 365 days/year + 8 days) out of the 11,574.074074 days.

So it will be 11,574.074074 - 11,323 =

251.074074daysinto the 31st year whentime_treaches 10 digits.Converting the .074074 days to hours, minutes, and seconds is as follows:

- .074074days * 24 hours/day =
1.7777777778hours.77777778hours * 60 minutes/hour =

46.666666667minutes.666666667minutes * 60 seconds/minute =

40secondsSo 31 years 251 days 1 hour 46 minutes and 40 seconds into the UNIX Epoch,

time_twill go to 10 digits.31 years after 00:00:00 January 1, 1970 UTC is 2001.

251 days into the year is the 9th of September for non-leap years like 2001.

So

time_twill become a 10 digit quantity onSeptember 9th at 1:46:40 a.m. UTC.

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