I am working on a VC++ project using MFC. There's a CTime object in my function that has a value of "10/11/2016 03:00:00".......something like that.
I want to subtract one second from the time part. So it will look like
"10/11/2016 02:59:59"
So for e.g., if the CTime value is "10/22/2016 07:45:50" then after subtraction by 1 second it should be "10/22/2016 07:45:49"
I tried,
CTime - 1, but this gives an error.
UPDATE:
I fixed this via,
time_t myTime= CTime.GetTime();
myTime= myTime - 1;
time_t gives the time in seconds and thus it's straight forward at this point.
To add or subtract to or from a CTime you need to use a CTimeSpan object to indicate the duration you want to add or subtract.
For example, to subtract a second:
CTime cNewTime = cOldTime - CTimeSpan(0, 0, 0, 1);
Related
Can anyone explain how to convert a Hex TimeDateStamp DWORD value into human readable format?
I'm just curious as to how a value such as 0x62444DB4 is converted into
"Wednesday, 30 March 2022 10:31:48 PM"
I tried googling of course and could not find any explanation. But there are online converters available.
But I'm just interested in converting these values for myself.
Your value is a 32-bit Timestamp.
Your datetime value is a 32-bit Unix Timestamp: The number of seconds since 1/1/1970.
See https://unixtime.org/
In most programming languages you can work with the hexadecimal notation directly.
Implementation should not be done by one person alone, since a lot of engineering goes into it. Leap years, even leap seconds, timezones, daylight savings time, UTC... all these things need to be addressed when working with a timestamp.
I have added my rough calculation below as a demonstration. Definitely use an existing package or library to work with timestamps.
See the JavaScript code below for demonstration.
There I multiply your value by 1000 because JavaScript works in Milliseconds. But otherwise this applies the same to other systems.
let timestamp = 0x62444DB4;
let dateTime = new Date(timestamp * 1000);
console.log('Timestamp in seconds:', timestamp);
console.log('Human-Readable:', dateTime.toDateString() + ' ' + dateTime.toTimeString());
// Rough output, just for the time.
// Year month and day get really messy with timezones, leap years, etc.
let hours = Math.floor(timestamp/3600) % 24;
let minutes = Math.floor(timestamp/60) % 60;
let seconds = Math.floor(timestamp) % 60;
console.log('Using our own time calculation:', hours + ':' + minutes + ':' + seconds);
I am using time.Time in go. to get time in seconds (the number of seconds elapsed since 1970's January 1) I am using
now := Time.now()
loc, err := time.LoadLocation(country.Timezone) // time zone in Asia/Dhaka
now = now.In(loc)
then,
seconds := now.Unix()
but the seconds giving seconds without adding the time zone seconds. it actually giving the seconds in UTC. My question is, how can I get seconds with added 6 hours ( asia/dhaka time zone is UTC+6)?
If you want current clock time's second part only use below code:
loc := time.FixedZone("some_common_name", 6*60*60)
ts := time.Now().In(loc).Second()
fmt.Println(ts)
If you want seconds from start of current year(like 01.01.1970)
loc := time.FixedZone("some_common_name", 6*60*60)
tp := time.Date(1970, 1, 1, 0, 0, 0, 0, loc)
ts := time.Now().Sub(tp).Seconds()
fmt.Printf("%v", ts)
In case, you want different time zone information, change offset value of time.FixedZone() functions. As, if you want GMT +5, then use 5*60*60 as offset value
I've read a number of posts and most of them are rightfully biased that Unix() time should be exactly that; meaning UTC. However, In my particular case others, like the TCL team, are a little loose. Both input and output allow the user to override the TZ. Furthermore the default TZ has it's own rules.
In my case I was not even using times... only dates. However, the closer to the date boundary the more likely it change days and thus bang up the date expressions etc.
In TCL there is UTC seconds from 1/1/1970 but there is also TZ adjusted seconds from 1/1/1970. (right or wrong I need some compatibility)
// parse the time string (the value does not have the TZ)
t, _ := time.Parse(format, value)
// set the location.
t = t.In(location)
// get the offset seconds from TZ
_, offset := t.Zone()
// adjust the Unix() seconds by the offset.
retval = fmt.Sprintf("%d", t.Unix()-int64(offset))
I'm in EST5EDT and it works here when location is EST5EDT and Local. I did not try anything on the other side of the UTC.
UPDATE: Well... Someone once said show me a programmer who knows dates and times and I'll show you someone who doesn't. The code above worked just fine as Local and UTC were on the same calendar day. But as soon as UTC moved into the next calendar day the Seconds were exactly 24hrs apart. I can squeeze the last second out of this so that TCL and my app work similarly but I'm better off doing this in the app code rather than in the libs.
I faced with an interesting problem with mktime function. I use russian time zone (UTC+03:00) Волгоград, Москва, Санкт-Петербург (RTZ 2) / Volgograd, Moscow, Saint Petersburg/ and try to construct time_t for "7.01.2009 00:00:00"
tm localTM;
localTM.tm_sec = 0;
localTM.tm_min = 0;
localTM.tm_hour = 0;
localTM.tm_mday = 7;
localTM.tm_mon = 0;
localTM.tm_year = 109;
time_t t = mktime(&localTM);
After mktime execution date&time is changed to "6.01.2009 23:00:00".
I have no problems then I construct time for "06.01.2009 00:00:00" or "08.01.2009 00:00:00".
If I switch time zone to another one, I get no problems with "7.01.2009 00:00:00".
What can be a reason of this oddity, and how can I workaround the issue?
When performing conversion to time_t, mktime needs to guess if the input is DST (Daylight Saving Time) or not.
For that, tm.tm_isdst field is used. See from man mktime
tm_isdst A flag that indicates whether daylight saving time is in
effect at the time described. The value is positive if day-
light saving time is in effect, zero if it is not, and nega-
tive if the information is not available.
Since you do not initialize tm_isdst in your code, the default value (0) is used, making mktime think it's in NO-DST period.
To fix it in your code, simply add
localTM.tm_isdst = -1
Note - that logic is necessary as for some moments in time just the "wallclock" information stored in tm is not sufficient to determine the exact time.
And yes, the fact that the default behavior is like that is a bit messed up :)
How would I be able to get the size or count of a range made up of Time objects?
Something that would achieve the same result as my pseudo Ruby code, which doesn't work:
((Time.now.end_of_day - 31.days)..(Time.now.end_of_day - 1.day)).size == 30
currently doing the above gives an error:
NoMethodError: undefined method `size' for 2012-05-18 23:59:59 -0400..2012-06-17 23:59:59 -0400:Range
and trying to turn it into array (range).to_a :
can't iterate from Time
update
Interesting, Just tried to do
((Date.today.end_of_day - 31.days)..(Date.today.end_of_day - 1.day)).count
Users/.../gems/ruby/1.9.1/gems/activesupport-3.0.15/lib/active_support/time_with_zone.rb:322: warning: Time#succ is obsolete; use time + 1
However
((Date.today - 31.days)..(Date.today - 1.day)).count == 31
I would be willing to settle for that?
Also ((Date.today - 31.days)..(Date.yesterday)).count == 31
update 2
On the other hand, taking Mu's hint we can do:
(((Time.now.end_of_day - 31.days)..(Time.now.end_of_day - 1.day)).first.to_date..((Time.now.end_of_day - 31.days)..(Time.now.end_of_day - 1.day)).last.to_date).count == 31
There's no such method as Range#size, try Range#count (as suggested by Andrew Marshall), though it still won't work for a range of Time objects.
If you want to perform number-of-days computations, you're better off using Date objects, either by instantiating them directly (Date.today - 31, for example), or by calling #to_date on your Time objects.
Date objects can be used for iteration too:
((Date.today - 2)..(Date.today)).to_a
=> [#<Date: 2012-06-17 ((2456096j,0s,0n),+0s,2299161j)>,
#<Date: 2012-06-18 ((2456097j,0s,0n),+0s,2299161j)>,
#<Date: 2012-06-19 ((2456098j,0s,0n),+0s,2299161j)>]
((Date.today - 2)..(Date.today)).map(&:to_s)
=> ["2012-06-17", "2012-06-18", "2012-06-19"]
It's because a size for a date range doesn't make sense—it doesn't know if you want to view it as days, minutes, seconds, months, or something else. The reason the error mentions iterating is that in order to determine the size of the range, it must know how to iterate over them so that it may count the number of elements.
Since what you want is the difference in days, just do that:
date_one = Time.now.end_of_day - 31.days
date_two = Time.now.end_of_day - 1.day
((date_one - date_two) / 1.day).abs
#=> 30.0
You must divide by 1.day since a difference of Times returns seconds.
To have any chance of your code working you should wrap everything before .size in parentheses.
Instead of using a range, maybe you can just subtract one time object from another?
I know you make ranges out of Date objects so you could convert to that.
I have 2 independent but contiguous date ranges. The first range is the start and end date for a project. Lets say start = 3/21/10 and end = 5/16/10. The second range is a month boundary (say 3/1/10 to 3/31/10, 4/1/10 to 4/30/10, etc.) I need to figure out how many days in each month fall into the first range.
The answer to my example above is March = 10, April = 30, May = 16.
I am trying to figure out an excel formula or VBA function that will give me this value.
Any thoughts on an algorithm for this? I feel it should be rather easy but I can't seem to figure it out.
I have a formula which will return TRUE/FALSE if ANY part of the month range is within the project start/end but not the number of days. That function is below.
return month_start <= project_end And month_end >= project_start
Think it figured it out.
=MAX( MIN(project_end, month_end) - MAX(project_start,month_start) + 1 , 0 )