On Sunday, July 4, 2021 at 1:09:10 PM UTC-7 [email protected] wrote:
> I have a filed that in a tiddler that has a date value, i would like to
> have button to add one hour to the date value , is this possible ?
>
By "date value", do you actually mean a full "datetime" value, which in TW
is stored as a 17-digit number (YYYYMMDDhhmmssXXX)? Assuming that is the
case, it can be done, but it's not as simple as it may seem.
For instance, if the stored datetime is 20210704133000000 (i.e., 1:30pm on
July 4, 2021), then it is relatively easy (though not trivial) to add an
hour, like this:
<$button> add an hour
<$vars
before={{{ [{!!stored_datetime}split[]first[8]join[]] }}}
hour={{{ [{!!stored_datetime}split[]rest[8]first[2]join[]] }}}
after={{{ [{!!stored_datetime}split[]rest[10]join[]] }}}>
<$vars newhour={{{ [<hour>add[1]pad[2]] }}}>
<$action-setfield stored_datetime={{{
[<before>addsuffix<newhour>addsuffix<after>] }}} />
</$vars>
</$vars>
</$button>
* First, break the datetime value into parts to isolate the hour number:
** Use split[] to break the datetime value into individual digits, and join
the first[8] digits to get the date portion.
** Use rest[8] to get the remaining digits and join the first[2] of those
digits to get the hour number.
** Use rest[10] to get the digits following the hour number, and join those
to get the minutes, seconds and millisecond portion.
* Next, add 1 to the hour number and apply pad[2] to the result to ensure
it is 2 digits with a leading 0 if needed.
* Then, reassemble the parts to give the new datetime value and update the
field value.
However... *this is not sufficient to handle all possible stored_datetime
values*.
For example, suppose that the stored datetime is 20210704233000000 (i.e.,
11:30pm on July 4, 2021). Simply adding an hour as shown above would give
20210704243000000. But that is not a valid datetime value, as the hours
portion must be between 00 and 23. The correct result would actually be
20210705003000000 (i.e., 12:30am on July 5, 2021). Thus, we need to handle
"hour overflow" to set the hour number to 00 and add 1 to the day number.
But... even that is not enough. Suppose the stored datetime is
20210731233000000 (i.e., 11:30pm on July 31, 2021). Then adding 1 hour
should result in 20210801003000000 (i.e., 12:30am on August 1, 2021). Thus,
we not only need to handle "hour overflow" as above, but also "date
overflow" to add 1 to the month number.
Complicating this is that the number of days per month varies, so the "date
overflow" handling needs to take into account the specified month to know
how many days it has. Further complicating this is leap years, in which
the number of days in February is 29 rather than 28, but only for years
that are divisible by 4 but not divisible by 100, unless also divisible by
400.
Lastly, we need also to handle "year overflow". If the stored datetime is
20211231233000000 (i.e., 11:30pm on December 31, 2021). Then adding 1 hour
should result in 20220101003000000 (i.e., 12:30am on January 1, 2022).
Obviously, handling all of these issues requires some complex conditional
calculations. Fortunately, *I've already tackled this problem
in http://tiddlytools.com/timer.html#TiddlyTools%2FTime%2FClocks*. The
clock_adjustForTimezone() macro takes the current datetime and adds or
subtracts a "timezone offset" value to give a new datetime value. For your
purposes, rather than using the current datetime, you want to get the
stored_datetime value, and instead of using a "timezone offset", you want
to use a specified offset of 1 hour (i.e., "+01:00")
Here's a modified version of clock_adjustForTimezone() that does what you
need:
\define adjust_time()
\whitespace trim
<!-- split time into parts -->
<$vars yyyy={{{ [<time>split[]first[4]join[]] }}}>
<$vars mm={{{ [<time>split[]first[6]last[2]join[]] }}}>
<$vars dd={{{ [<time>split[]first[8]last[2]join[]] }}}>
<$vars hh={{{ [<time>split[]first[10]last[2]join[]] }}}>
<$vars min={{{ [<time>split[]first[12]last[2]join[]] }}}>
<$vars ssxxx={{{ [<time>split[]last[5]join[]] }}}>
<!-- apply offset "+hh:mm" or "-hh:mm" -->
<$vars sign={{{ [<offset>split[]first[]] }}}>
<$vars offhh={{{ [<offset>split[]first[3]join[]] }}}>
<$vars offmin={{{ [<offset>split[]last[2]join[]addprefix<sign>] }}}>
<$vars hh={{{ [<hh>add<offhh>] }}}>
<$vars min={{{ [<min>add<offmin>] }}}>
<!-- adjust days per month for leap year -->
<$set name="leap" value={{{ [<yyyy>remainder[4]match[0]then[yes]] }}}>
<$set name="dpm" value="31 28 31 30 31 30 31 31 30 31 30 31"> <!-- days
per month -->
<$set name="dpm" filter="[<leap>!match[]]" value="31 29 31 30 31 30 31 31
30 31 30 31" emptyValue=<<dpm>>>
<!-- adjust hours/minutes for minutes wraparound -->
<$set name="hh" filter="[<min>compare:integer:lt[0]]" value={{{
[<hh>subtract[1]] }}} emptyValue=<<hh>>>
<$set name="hh" filter="[<min>compare:integer:gteq[60]]" value={{{
[<hh>add[1]] }}} emptyValue=<<hh>>>
<$set name="min" filter="[<min>compare:integer:lt[0]]" value={{{
[<min>add[60]] }}} emptyValue=<<min>>>
<$set name="min" filter="[<min>compare:integer:gteq[60]]" value={{{
[<min>subtract[60]] }}} emptyValue=<<min>>>
<!-- adjust date/hours for hours wraparound -->
<$set name="dd" filter="[<hh>compare:integer:lt[0]]" value={{{
[<dd>subtract[1]] }}} emptyValue=<<dd>>>
<$set name="dd" filter="[<hh>compare:integer:gteq[24]]" value={{{
[<dd>add[1]] }}} emptyValue=<<dd>>>
<$set name="hh" filter="[<hh>compare:integer:lt[0]]" value={{{
[<hh>add[24]] }}} emptyValue=<<hh>>>
<$set name="hh" filter="[<hh>compare:integer:gteq[24]]" value={{{
[<hh>subtract[24]] }}} emptyValue=<<hh>>>
<!-- adjust month/date for date wraparound -->
<$set name="dm" value={{{ [<dpm>split[ ]nth<mm>] }}}> <!-- days in this
month -->
<$set name="mm" filter="[<dd>compare:integer:lteq[0]]" value={{{
[<mm>subtract[1]] }}} emptyValue=<<mm>>>
<$set name="mm" filter="[<dd>compare:integer:gt<dm>]" value={{{
[<mm>add[1]] }}} emptyValue=<<mm>>>
<$set name="dd" filter="[<dd>compare:integer:lteq[0]]" value={{{
[<dpm>split[ ]nth<mm>] }}} emptyValue=<<dd>>>
<$set name="dd" filter="[<dd>compare:integer:gt<dm>]" value={{{ [[1]]
}}} emptyValue=<<dd>>>
<!-- adjust year/date/month for month wraparound -->
<$set name="yyyy" filter="[<mm>compare:integer:lteq[0]]" value={{{
[<yyyy>subtract[1]] }}} emptyValue=<<yyyy>>>
<$set name="yyyy" filter="[<mm>compare:integer:gt[12]]" value={{{
[<yyyy>add[1]] }}} emptyValue=<<yyyy>>>
<$set name="dd" filter="[<mm>compare:integer:lteq[0]]" value={{{
[[31]] }}} emptyValue=<<dd>>>
<$set name="dd" filter="[<mm>compare:integer:gt[12]]" value={{{ [[1]]
}}} emptyValue=<<dd>>>
<$set name="mm" filter="[<mm>compare:integer:lteq[0]]" value={{{
[[12]] }}} emptyValue=<<mm>>>
<$set name="mm" filter="[<mm>compare:integer:gt[12]]" value={{{ [[1]]
}}} emptyValue=<<mm>>>
<!-- zero-pad and assemble new time -->
<$vars mm={{{ [<mm>pad[2]] }}} dd={{{ [<dd>pad[2]] }}} hh={{{
[<hh>pad[2]] }}} min={{{ [<min>pad[2]] }}}>
{{{
[<yyyy>addsuffix<mm>addsuffix<dd>addsuffix<hh>addsuffix<min>addsuffix<ssxxx>]
}}}
\end
and here's a button that invokes the above to update the stored_datetime
field value:
<$button> add an hour
<$vars time={{!!stored_datetime}} offset="+01:00">
<$wikify name="newtime" text=<<adjust_time>>>
<$action-setfield stored_datetime=<<newtime>> />
</$wikify>
</$vars>
</$button>
enjoy,
-e
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