I was testing a feature where I had to write a record with created_at field which is of type time.Time into a Mysql table. When I read the same record back I get following diff.
Time: (time.Time) {
- wall: (uint64) 454722000,
+ wall: (uint64) 0,
What is wall in golang Time and why are they different?
The Monotonic Clocks section of the time package documentation describes monatomic and wall clock time in detail. The section covers the scenario of reading a time from a database.
See Equal for information on how to compare time values.
The real reason for me has to do with nano seconds. Apparently when I write to db nano seconds are stripped off. So what I did is created a function that would return me current time but without nano seconds.
Related
I need to find a difference in minutes between the time from a database retrieved by Ecto and current time, in UTC. As far as I know, timing operating on Elixir aren't trivial without using third-party libraries such as Timex. I, however, want to avoid using third-party dependencies. So how can I find a time difference? I know I can get the current time by DateTime.utc_now(), but what's next, how to subtract a date-time from a database, which is in Ecto.DateTime format, from it?
I believe there are plans soon for Ecto to use the native Elixir Datetime format for the time being, I know your pain.
One solution is to convert the ecto date time to the erlang date time format:
{{YYYY, MM, DD}, {HH, MM, SS}}
And then compare that using the erlang calendar library. For example, say we had a Post model and we wanted to know how long ago it was updated:
Repo.Post.get!(%Post{}, 1).created_at
|> Ecto.DateTime.to_erl
|> :calendar.time_difference(:calendar.universal_time)
So let's say this post was created roughly 1 month ago (2016-10-25T10:24:23).
Running it through the above function would return:
{30, {17, 30, 53}}
Meaning 30 days, 17 hours, 30 minutes and 53 seconds ago.
You can easily from there destructure the tuple and take only the components you need (in your case the minutes).
E.g.
{_, {_h, minutes, _s}} = time_diff
Banging my head on this simple date logic problem:
I know the user's time zone offset relative to UTC.
My server is in UTC. It knows the time now.
How do I calculate UTC equivalent of 'yesterday local time at 8am'?
IN JS, I tried to do it this, but it seems to not quite work.
var yesterday_am=moment(moment(new Date()).subtract(24,'hour')).format('YYYY-MM-DD'); // same local time previous day;
// when is 8am local time in utc?
var am=8 - (user.tz_offset/60);
if (am<0) { yesterday_am=moment(yesterday_am).subtract(Math.abs(am), 'hour')};
if (am>0) { yesterday_am=moment(yesterday_am).add(am, 'hour')};
For example, if UTC is 2016-01-10 0235 and local time is -7 hours, it would output 2016-1-09 1500 (8am local).
The logic you are trying to perform is impossible. Without knowing the user's actual time zone, you cannot know the UTC equivalent of 'yesterday at 8 am' local time. Daylight saving time transitions may make the offset yesterday different than the offset today. See the time zone tag wiki, particularly the Time Zone != Offset section for more information.
If you do know the user's time zone, then you can perform this calculation using the moment timezone add-on library for Moment.js. The code would be as follows:
moment().tz('America/Los_Angeles').subtract(1, 'day')
.set({hours:8, minutes:0, seconds:0, milliseconds:0}).utc()
Breaking this down so it makes sense, we are doing the following things:
moment() //get the current time
.tz('America/Los_Angeles') //put the moment in the Los Angeles time zone
//the Los Angeles time zone is one of several that are UTC-7 right now
.subtract(1, 'day') //go to yesterday
.set({hours:8, minutes:0, seconds:0, milliseconds:0}) //set the time to exactly 8 am
.utc() //convert back to UTC
Do not add 8 hours to the start of the day. This will be 9 AM if the clocks 'sprang forward' that day, and 7 am if they 'fell back'.
It sounds like your code is running in Node on the server. If it is running in the browser, then the browser knows the user's time zone rules, and you could use the following code to get the time at 8 am yesterday:
moment().subtract(1, 'day').set({hours:8, minutes:0, seconds:0, milliseconds:0}).utc()
This code does not require the moment timezone add on because the browser knows the time zone rules for the user's local time.
If you need to get the user's time zone, you have a few options. The most reliable is to use a timezone picker built into a map to let the user choose. There are a few of these floating around the internet.
If you do not want to do that, you can use the moment.tz.guess() function to have moment timezone make an educated guess about the user's time zone using some heuristics. This function is good, but due to limitations of the browser it is impossible to make it 100% accurate.
For a whole bunch of information about handling date and time and time zones in JavaScript, you can try this talk I did at JavaScript MN a few months ago.
In addition, you might like this really excellent Pluralsight course by Matt Johnson.
This code is not DST aware (in case if you've not already figure out based on the comments below). Thank you Maggie. Please refer to complete answer from Maggie.
You can do something like this
var localTime = moment.utc("2016-06-19").utcOffset('-07:00');
var utcAt8PrevDay = moment(localTime).subtract(1,'days').startOf('day').add(8, 'hour').utc();
I am writing a python script which mainly involves decoration of console output.
I have some value called expiration_time which is in milliseconds. When I display expiration_time on console it is hard to find how much time exactly left to expire. User needs to do some calculation to know how much time is left.
So I decided to print epoch time instead. I want to do something like this:
epoch_time_at_which_expiration_will_happen = current_epoch_time + expiration_time_in_milliseconds
I want to output epoch_time_at_which_expiration_will_happen. How can I do it?
Not really sure what you are trying to output, the time at which expiration happens or the time until the expiration?
Either way, I would use a datetime object instead of the epoch time and convert the milliseconds to microseconds. The datetime objects allow you to do the math you want and to display the output formatted nicely.
https://docs.python.org/2/library/datetime.html
Let's say I have a task execute. I want to know according to the system clock/time when that finished executing. Is there something in Java I can use to pull the current system time and display it in Java? I'm not looking to measure time like using Millis or Nano (that would only tell me how many milliseconds, not the actual time or date), but actually print the time finished (like "Finished at 9:42 P.M. 10/14/2012" as per my actual Windows time).
A quick Google search finds this: http://www.mkyong.com/java/java-how-to-get-current-date-time-date-and-calender/
Just make sure you import java.util and java.text, and you should be good to go.
To clarify, I mean time spent while the system is suspended/hibernated, not the calling thread (GetTickCount() returns the number of milliseconds since system boot).
As far as I know, GetTickCount is unrelated to threads and counts the time since the system has started. But it is better to use GetTickCount64 to avoid the 49.7 day roleover.
By the way, to get what you want you need the GetThreadTimes function. It records the creation and exit time and the amount of time the thread has spend in user or kernel space. So you have a nice way to calculate the amount of time spend.
Ok, I missed the "system" part of the question. But that is simple. When in hibernation GetTickCount continues the counting. Because people have suffered from the 49.7 days bug when the computer was in hibernate most of the time. See link text here for more information.
Short answer : Yes.
Longer answer: Read the GetTickCount() docs: It's the elapsed time since system startup, and even MS wouldn't suggest that time stands still while your computer is hibernating...
Yes, GetTickCount does include suspend/hibernate time.
In the following python script I call the Sleep API to wait 40 seconds to give me a chance to put the computer into hibernate mode, and I print the time before and after, and the tick count difference after.
import win32api
import time
print time.strftime("%H:%M:%S", time.localtime())
before = win32api.GetTickCount()
print "sleep"
win32api.Sleep(40000)
print time.strftime("%H:%M:%S", time.localtime())
print str(win32api.GetTickCount()-before)
Output:
17:44:08
sleep
17:51:30
442297
If GetTickCount did not include the time during hibernate it would be much less than the time I hibernated for, but it matches the actual time elapsed (7 minutes 22 seconds equals 442 seconds, i.e. 442000 millisecond "ticks").
For any one looking for answer under Windows CE platform, from docs:
http://msdn.microsoft.com/en-us/library/ms885645.aspx
you can read:
For Release configurations, this function returns the number of
milliseconds since the device booted, excluding any time that the
system was suspended. GetTickCount starts at 0 on boot and then counts
up from there.
GetTickCount() gives you the time in milliseconds since the computer booted. it has nothing to do with the process calling it.
No, GetTickCount() does not include the time the system spend during hibernate.
A simple test proves this.
in Python:
import win32api
win32api.GetTickCount()
-- do hibernate --
win32api.GetTickCount()
and you'll see the result...