Re: "two time periods with only an endpoint in common do not overlap" ???

On 10/15/21 8:59 AM, Adrian Klaver wrote:
> On 10/15/21 06:52, Ron wrote:
>> On 10/14/21 7:02 PM, Adrian Klaver wrote:
>> [snip]
>>> or the third example in the docs:
>>>
>>> SELECT (DATE '2001-02-16', DATE '2001-12-21') OVERLAPS
>>>        (DATE '2001-10-30', DATE '2002-10-30');
>>> Result: true
>>> SELECT (DATE '2001-02-16', INTERVAL '100 days') OVERLAPS
>>>        (DATE '2001-10-30', DATE '2002-10-30');
>>> Result: false
>>> SELECT (DATE '2001-10-29', DATE '2001-10-30') OVERLAPS
>>>        (DATE '2001-10-30', DATE '2001-10-31');
>>> Result: false
>>
>> Why /don't/ they overlap, given that they share a common date?
>
> Per the docs:
>
> https://www.postgresql.org/docs/current/functions-datetime.html
>
> " Each time period is considered to represent the half-open interval start 
> <= time < end, unless start and end are equal in which case it represents 
> that single time instant."
>
> Which I read as
>
> (DATE '2001-10-29', DATE '2001-10-30') ends at '2001-10-29'
>
> and
>
> (DATE '2001-10-30', DATE '2001-10-31') starts at DATE '2001-10-30'
>
> so no overlap.

I was afraid you were going to say that.  It's completely bizarre, but seems 
to be a "thing" in computer science.

-- 
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