I have two NSDate objects. One (call it date1) has timestamp in the future i.e 2012-07-16 12:00 and also this date is repeating daily. The other one (date2) has a timestamp also in the future i.e 2012-07-17 12:00.
Now I want to check if possibly date1 will clash with date2. Obviously it will not clash at 2012-07-16 12:00 but the day after (since it's repeating daily) it will clash with date2.
How could I implement this check?
First check if the events would overlap on any date, i.e. using only the starting time and length of the events. If they do, then check if the dates are the same, or if the earlier of the dates is for an event that repeats enough times to occur on the date of the second event.
To compare the times you can use something like this to extract the hours and minutes from the NSDates: How do I get hour and minutes from NSDate?
For the second check you can first use NSDate's compare, followed by a timeIntervalSinceDate which you feed into something like this: How do I break down an NSTimeInterval into year, months, days, hours, minutes and seconds on iPhone? to get the number of days between the two dates, which you then can compare against the repeat count of the event.
Related
is it possible to have date_diff with specific start and end time?
let say my store are open from 8AM - 10PM, which is 14 Hours.
and I have a lot of stuff to sell during that time. One of the SKU is out of stock from 2022-11-01 06.00 PM until tomorrow 2022-11-02 11.00 AM.
Instead of calculate 24 hours, I just want to calculate only from opening store until it closed or until its restock. Meaning from 6PM to 11AM is 8 Hours
my query
select date_diff('2022-11-02 11.00 AM', '2022-11-02 06.00 PM', hour) from table
with the result 17 hours instead of 8 hours
There isn't a way to configure DATE_DIFF to do this for you, but it's possible to do what you want, with some effort.
You should convert your dates to timestamps (TIMESTAMP(yourdate) or CAST(yourdate AS TIMESTAMP)) and use TIMESTAMP_DIFF instead.
This will allow you to work with smaller intervals than days.
For your calculation, you ultimately need to find the total time difference between the two timestamps and then subtract the out-of-hours timeframe.
However, calculating the latter is not as simple as taking the difference in days and multiplying by 8 hours (10pm-6am), because your out-of-hours calculation has to account for weekends and possibly holidays etc. Hence it can get quite complex, which is where the solution in my first link might come in.
I have a table where each entry has a timestamp. I am using this timestamp to calculate e.g. the number of entries per day in the last week. However, I do not really care whether the results that I get represent a particular day. The actual goal is to divide the entries into 24h-bins that I can compare and see whether there has been any significant change over time. Furthermore, since I am working with almost real-time data, I would like to perform this analysis at any time and also take into account the most recent entries. If I would just group the entries per day and perform the query in the middle of the day then I would get a not particularly insightful result for the current day.
My idea was now to subtract the current time from the timestamp of the entries and then do the grouping by days. This way I could get 24h-bins each of which represents a full 24h period and the youngest one also contains the most recent entries.
Something like this:
created_on - current_time
Of course I cannot subtract a time from a timestamp. Is there a way to convert current_time into an interval? Or is there an entirely different approach that is easier?
Is there a way to convert current_time into an interval?
Yes, just cast it.
Note that the use of current_time is discouraged so it's better to use localtime instead.
You can do:
created_on - localtime::interval
But it seems you might just want to set the time part of the timestamp to 00:00:00 which you can do by using date_trunc()
date_trunc('day', created_on)
I would like to check if the processed date is today.
xsl:if test="ProcessedDate = 'Today'" won't work since the value of processed date is a timestamp more like 2016-06-07T09:06:54.827z
How can I mathematically convert it to check the processed date to see if it's in the past 24 hrs.
Perhaps within a ().
I have a table described here: http://sqlfiddle.com/#!3/f8852/3
The date_time field for when the time is 00:00 is wrong. For example:
5/24/2013 00:00
This should really be:
5/23/2013 24:00
So hour 00:00 corresponds to the last hour of the previous day (I didn't create this table but have to work with it). Is there way quick way when I do a select I can replace all dates with 00:00 as the time with 24:00 the previous day? I can do it easily in python in a for loop but not quite sure how to structure it in sql. Appreciate the help.
All datetimes are instants in time, not spans of a finite length, and they can exist in only one day. The instant that represents Midnight is by definition, in the next day, the day in which it is the start of the day, i.e., a day is closed on its beginning and open at its end, or, to phrase it again, valid allowable time values within a single calendar date vary from 00:00:00.00000, to 23:59:59.9999.
This would be analogous to asking that the minute value within an hour be allowed to vary from 1 to 60, instead of from 0 to 59, and that the value of 60 was the last minute of the previous hour.
What you are talking about is only a display issue. Even if you could enter a date as 1 Jan 2013 24:00, (24:00:00 is not a legal time of day) it would be entered as a datetime at the start of the date 2 Jan, not at the end of 1 Jan.
One thing that illustrates this, is to notice that, because of rounding (SQL can only resolve datetimes to within about 300 milleseconds), if you create a datetime that is only a few milleseconds before midnight, it will round up to midnight and move to the next day, as can be seen by running the following in enterprise manager...
Select cast ('1 Jan 2013 23:59:59.999' as datetime)
SQL server stoers all datetimes as two integers, one that represents the number days since 1 Jan 1900, and the other the number of ticks (1 tick is 1/300th of a second, about 3.33 ms), since midnight. If it has been zero time interval since Midnight, it is stll the same day, not the previous day.
If you have been inserting data assuming that midnight 00:00:00 means the end of the day, you need to fix that.
If you need to correct your existing data, you need to add one day to every date in your database that has midnight as it's time component, (i.e., has a zero time component).
Update tbale set
date_time = dateAdd(day, 1, date_time)
Where date_time = dateadd(day, datediff(day, 0, date_time), 0)
I have an NSArray of CFAbsoluteTimes. They should be sorted from earliest to latest, but if not I can sort them.
What I need to do is find the min and max date (e.g. Jan 1 to Jan 5) and create a bucketization that shows the count for each day between, e.g.:
Jan 1 - 1
Jan 2 - 0
Jan 3 - 4
Jan 4 - 0
Jan 5 - 3
Something like that. What is the simplest way to turn the absolute times into a rounded NSDate of some sort I can count? Intermediate forms don't really matter to me. I just need to write a function that returns a count when given a date.
You'll probably be happier working completely in Cocoa for this problem, using NSDate instead of CFAbsoluteTime.
Applicable document is the Date and Time Programming Guide.
The general approach you'll need is to work within an NSCalendar, which encapsulates all of the information about days per month, months per year, leap years, DST changes, all for a particular time zone. Convert your NSDate instances to NSDateComponent and you'll be able to extract the day and month numbers, then bucketize from there.
Remember that the function you write (return a count when given a date) will implicitly or explicitly have to handle NSCalendar and NSTimeZone values. The answer will vary by year (is it a leap year? does the interval include a leap day) and locale/date (are we observing Daylight Saving Time in this location right now?).