[tz] Request RE: academic research question re: TZ database

Paul Gilmartin PaulGBoulder at AIM.com
Thu Jan 9 22:15:42 UTC 2020

> On 2020-01-09, at 14:39:58, Paul Eggert <eggert at cs.ucla.edu> wrote:
> On 1/9/20 6:15 AM, Andrew Lyon wrote:
>> if the hour of birth is unknown (for patients born 1930-41), that a birth hour of midnight is assigned as a default.
> If the birth hour is unknown you might be better off defaulting to noon than to midnight. First, noon is likely closer to the actual birth hour.[1] Second, you'll avoid some of these software glitches.
> [1] https://www.cdc.gov/nchs/products/databriefs/db200.htm
Indeed.  I don't know if this is relevant:

    The mktime() function shall return the specified [local] time
    since the Epoch encoded as a value of type time_t. If the time
    since the Epoch cannot be represented, the function shall
    return the value (time_t)-1 [CX]   and set errno to indicate
    the error.

Does this refer to times during the spring-forward hour?  Should
mktime() then return the nearest boundary and set errno?

There's an unfortunate design choice since time_t is generally
regarded as signed (citation needed) and (time_t)-1 might
represent 1969-12-31 23:59:59.  The programmer must check errno.

-- gil

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