I'm using flutter. In which way a DateTime should be stored in firestore so that I can make a filter based on the DateTime. Should it be converted to String or something else? What is the perfect way here?
Firestore has a native Timestamp type that can be used to store timestamps, which:
A Timestamp represents a point in time independent of any time zone or calendar, represented as seconds and fractions of seconds at nanosecond resolution in UTC Epoch time
This type is perfectly suited for filtering on date/time ranges, for example when you want to get all documents with a field between January 7, 2021 at 7:41:00AM and January 20, 2021 at 2:00:42PM.
In cases where I'm purely interested in a date and not in a time, I often store that as a string in "20210107" format (so yyyyMMdd). I find this format slightly easier when I want to get documents for a specific date, as I can use an equality filter. But the trade-off is that I love the precision of time. As you can probably guess from my phrasing this is a personal preference, not necessarily a best way for all cases or everyone.
It must be a string, you can split or format it as the day / month / year you want after the string value
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Good day all,
I am trying to filter todays result in SQL table to a collection in powerapps. The column "dt" represents the column in sql of datetime type.
This is my powerapps filter:
ClearCollect(myCollectionName, Filter(myDatasource, Text(dt,"dd/mm/yyyy") = Text(Now(),"dd/mm/yyyy" )));
Seems like the collection is still empty even there is data for today in sql. May I know if my approach is the correct way in filtering?
Short answer: the data is likely being changed based on the client time zone. To fix it, you can update it by applying the time zone offset to the data from the SQL table, something along the lines of:
ClearCollect(
myCollectionName,
Filter(
myDatasource,
Text(DateAdd(dt, TimeZoneOffset(dt), Minutes), "dd/mm/yyyy") =
Text(Now(), "dd/mm/yyyy")))
Long(er) answer: the datetime type in SQL Server represents an absolute value of date and time. For example, the value '2021-12-23 09:30:00' represents 9:30 in the morning of the 23rd day of December, 2021 - at any part of the world. The date/time type in Power Apps, however, represents a point in time, typically referring to the local time where the app is being executed (or created). For example, if I selected that value and I'm in the US Pacific Time Zone (UTC-08:00), that would represent the same value as if someone in London (UTC+00:00) selected 2021-12-23 17:30:00. Since the two types represent different concepts, we may have mismatches like you are facing. To fix this, we can either use a type in SQL Server that has the same semantics as Power Apps (for example, 'datetimeoffset'), or adjust the time when it is being transferred between SQL and Power Apps.
The blog post at https://powerapps.microsoft.com/en-us/blog/working-with-datetime-values-in-sql explains in more details how to work with date/time values in SQL and Power Apps.
I exported data from an SQLite table to a CSV file. The data includes a timestamp with at least one-minute resolution: "2019-11-15 01:30:06". The data is actually stored as a Julian date, in this case 2458802.35424295. I imported the data into a double-precision field. I need to convert that number into a timestamp with time zone. I tried casting the double-precision number to text and then using to_timestamp(), but that appears to work only with integer days. I can get a timestamp, but it is always at midnight of the correct date. I tried using to_timestamp() passing in my number, but that returns an epoch (number of milliseconds since 1/1/1970).
I could try to take the fractional part of my Julian date value, calculate the number of milliseconds since midnight that represents, use the to_timestamp(text,text) method to get the date I need, and then add the epoch since midnight to that date. But that's awfully cumbersome. Isn't there a better way?
I'm using PostgreSQL 9.3.
NOTE: The simple answer to my problem, which occured to me just before I clicked the Post button, is to export the data in the form I want, using SQLite's datetime() function to convert the number to a date string during export. But I remain curious. I would have thought there would be a standard way to do this conversion.
We are defining a microservice that returns a timestamp in the combined date-and-time ISO 8601 format which is returned to our iOS client that's written in Swift. In our client, this is converted to a Date object.
The issue is one of the feeding sources of our microservice represents their date/times as two separate fields which we must combine into the complete ISO format. However, the time portion may be null so we have to substitute in 'T00:00:00Z'.
The problem is we need a way to communicate to the Swift side that the timestamp didn't have an original time value so it should be read in relative to GST, not the local timezone as one would normally do, and it should only ever be displayed in the UI as a date-only.
That said, what is the proper way to flag a Date object as being Date-only? Our current solution is a paired xIsDateOnly boolean on the model, but that just seems verbose. Does the Date object have any such mechanism/indication? I'm guessing not because a date without a time doesn't actually make sense as dates are based on 12am in a particular timezone, usually implied to be the one the user is in.
You're right, the Foundation (NS)Date object is really a timestamp, representing a specific moment in time. While it doesn't let you just specify a particular day, it does have the advantage of being the same no matter what calendar is in use.
To represent something like "June 3, 2014", you can use a DateComponents object. This lets you specify month, day, year, etc, without a time of day, relative to a particular calendar.
I have to convert IST(India) to EET(Finland) timing using perl or shell ...
Means i have to subtract 3 hours,30 minutes from a given specific (ISD)time (not from the current time).
Time is in this format: YYYY-MM-DD HH:MM:SS
For ex: IST: 2016-01-01 02:30:00
Then after subtracting 3hours and 30 minutes ,I should get,
EET: 2015-12-31 23:00:00
The thing is after subtracting,if required the date,month and year should also change.
Can i do this using perl? Can anyone help me on this?
I'm not going to give you the actual code as you haven't demonstrated that you have made any effort to solve this yourself.
But the way to do this is to use a real Date/Time handling library. In Perl, that probably means DateTime. You can use DateTime::Format::Strptime to generate a DateTime object from a string.
In summary, your approach should be:
Parse your string into a DateTime object (being careful to ensure that the parsing object knows that the time zone is ISD (Icelandic time, I assume [Update: or, more likely, Indian]).
Convert the time zone in your parsed object to EET.
Use the parsed object's strftime method to produce the output time in the correct output.
Update: And I'll just add the standard advice about handling dates and times. You should always transmit and store dates and times in UTC. Local time zones should only every be displayed to users.
I have various timestamps stored in Mongo collections, some as floats and some as ints.
They are all stored in BST and the server will be switched to UTC soon. How do I convert them within Mongo to be UTC timestamps?
In MySQL I can do this:
UPDATE `table` SET `field` = CONVERT_TZ(`field`, 'Europe/London', 'UTC');
Is there a Mongo equivalent?
You'll have to use your language of choice and update them one at a time. It should be as simple as a for loop that loads the data and rewrites it.
Just double-check how your language of choice handles timestamps across timezones. Making such a data change can have all kinds of unexpected effects on production code.
Timestamps are generally in UTC and not in a specific timezone. All date/time libraries I've worked with return timestamps that are the number of seconds (or milliseconds) since Jan 1st 1970 UTC. Check the documentation for the library you used to create the timestamp to be sure.
This means that you should be ok, unless you have used a date/time library that does not follow this convention, or somehow calculated the timestamps yourself and accounted for the timezone.
For example in JavaScript if you store the value returned from new Date().getTime() and later pass that value to new Date(...) on a different system you will end up with the same absolute date/time, regardless of the timezones of the two systems. The same goes for Ruby, do Time.new.to_i on one machine, and run Time.at(...) on another and you will get the same absolute date/time. When I say "absolute date/time" I mean that it's UTC time will be the same, most likely the system will display it in the local time zone, but that is what you want.
Some points to consider about date in Mongo:
All dates are stored in UTC in MongoDB
MongoDB stores dates internally as a 64 bit integer representing
milliseconds since 1970-01-01T00:00:00Z
If the date value you provide is not already in UTC it
will be converted to UTC before being stored in MongoDB by the driver
The recommendation is not to use DateTime.Parse.
You will get into all sorts timezone issues regarding how DateTimes are formatted.
Instead just use one of the DateTime constructors with UTC flavor.
Example:
var dateTime = new DateTime(2011, 5, 5, 0, 0, 0, DateTimeKind.Utc);
Hope you find it useful.