Re: Date Comparison and Manipulation Functions?

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  • Hendrik van Rooyen

    Re: Date Comparison and Manipulation Functions?


    John Machin <sj..con.netwro te:
    >On Aug 30, 10:41 am, "W. eWatson" <notval....cglo bal.netwrote:
    >
    >What I'm trying to do is adjust date-time stamped file names for date and
    >time errors. The software program collects through a period that roughly
    >coincides with night hours every day and according to the OS clock. It
    >sometimes happens that a user sets the clock to the wrong day or hour,
    >possibly both. Possibly even the month or year. I'm trying to allow a user
    >the opportunity to repair the problem. (Date-time stamp part of the name is
    >yyyymmdd_hhmms s.) Correcting the date needs to be done easily and
    >accurately. For example, if on August 25, he mistakenly sets the date to
    >July 25, and discovers this problem on the real Oct. 5, he should be able to
    >shift all dates from July 25 through Sept. 5 to Aug. 25 through early Oct.,
    >allowing for day oddities in a month during the period. (I hope I got those
    >dates right; otherwise, I think you get the idea. In other words, he needs
    >to shift about 40 days of data to the correct dates.)
    >
    >... all of which is absolutely nothing to do with your surprise at the
    >result of whatever.plus(m onths=6).
    >
    >So for some period from recorded date X to recorded date Y, the
    >recorded dates of out of kilter by D days. X = Jul 25 2008, Y Sep 5
    >2008, and D is 31 (days from Jul 25 to Aug 25). All you have to do is
    >(pseudocode) :
    >
    >if X <= recorded_date <= Y:
    >new_recorded_d ate = recorded_date.p lus(days=D)
    >
    This will work nicely for negative values of D.
    The case of positive D values is more of a toffee:

    Its Wednesday and I make some observations.
    Its Thursday and I "fix" my clock - system thinks its Wednesday again.
    I make some observations - Either overwriting or adding to the
    original Wednesdays stuff.
    Its Friday and I spot the error - my D value is 1 day.
    I need to split the "Wednesday" file into two bits, if I can,
    and apply the correction to the second half, else I will have
    a gap for Wednesday.

    Depending on how the logging is done, it may be an unchewable toffee.

    - Hendrik



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