Ruby - I need to convert string into a timestamp - ruby-on-rails

I need to convert a string that represents a date to a timestamp object in Ruby.
For example:
date_string = "18-Feb-2016 09:01:04"
convert to a timestamp like so
2016-02-18 14:01:04
I need to save this to a mysql database were the column is type timestamp.
I have researched this for most of the day and can not find a solution. I know you can use Time.parse but that includes timezone and DateTime.parse().to_time includes the timezone. Since it has to be a timestamp i can not use strftime method.
I need the time to be included because it will be used for calculation purposes.
Any help would be greatly appreciated.
Thank you

TL;DR
datetime = DateTime.parse("18-Feb-2016 09:01:04").to_s(:db)
returns
"2016-02-18 09:01:04"
Here's a quick explanation...
1. Convert your string to a Date object with DateTime.parse
You can use the .parse method from the Date or DateTime class in order to parse a string. The parse method will return a Date object like this:
$ DateTime.parse("18-Feb-2016 09:01:04")
$ => #<DateTime: 2016-02-18T09:01:04+00:00 ((2457437j,32464s,0n),+0s,2299161j)>
.parse is a method provided by Ruby.
2. Format the string with DateTime.parse.to_s
Ruby on Rails gives you access to the DateTime.to_formatted_s method to change the formatting of the Date object prior to storing it in your database.
To match the format that you specified:
$ datetime = DateTime.parse("18-Feb-2016 09:01:04").to_formatted_s
Note: to_s is aliased from to_formatted_s and to_formatted_s is a method provided by Rails, not Ruby.

Use to_datetime method in Rails.
"12-10-2015".to_datetime
=> Mon, 12 Oct 2015 10:36:00 +0000
http://apidock.com/rails/String/to_datetime
Edited to add precise answer.

You can use .to_time or .to_datetime, the .to_time returns the date and time with timezone but the .to_datetime returns full date with week name but it shows +0000 as timezone, you will see the difference in both the formats, see the following example.
# used .to_time
"18-Feb-2016 09:01:04".to_time
## Output
2016-02-18 09:01:04 +0530
# used .to_datetime
"18-Feb-2016 09:01:04".to_datetime
## Output
Thu, 18 Feb 2016 09:01:04 +0000

I've interpreted the question to be that you wish to convert the string "18-Feb-2016 09:01:04" to the string "2016-02-18 14:01:04" (generalized to arbitrary date-time strings, of course).
Let:
str = "18-Feb-2016 09:01:04"
What you want is done in two steps. The first is to convert this string to a DateTime object, that is, an instance of the class DateTime. The second step is to construct the desired string from the DateTime object.
One way to create the DateTime object is to use the method DateTime::parse:
require 'date'
DateTime.parse(str)
#=> #<DateTime: 2016-02-18T09:01:04+00:00 ((2457437j,32464s,0n),+0s,2299161j)>
That works fine for the string format you gave, but can be problematic with other formats. For example:
DateTime.parse "4-5-16 09:01:04"
#=> #<DateTime: 2004-05-16T09:01:04+00:00 ((2453142j,32464s,0n),+0s,2299161j)>
As long as you know the format that will be used, it's generally better to use DateTime#strptime with the appropriate pattern comprised of format directives:
pattern = "%d-%m-%y %H:%M:%S"
DateTime.strptime("4-5-16 09:01:04", pattern)
#=> #<DateTime: 2016-05-04T09:01:04+00:00((2457513j,32464s,0n),+0s,2299161j)>
See DateTime#strftime for the format directives.
For the problem at hand:
dt = DateTime.strptime(str, "%d-%b-%Y %H:%M:%S")
#=> #<DateTime: 2016-02-18T09:01:04+00:00 ((2457437j,32464s,0n),+0s,2299161j)>
The second step is to construct the desired string with the above-referenced strftime method:
dt.strftime("%Y-%m-%d %H:%M:%S")
#=> "2016-02-18 09:01:04"

Related

Ruby date time parse to get 'th'

I've got date as string '2020-02-10 8,00' which I want to convert into Monday, 10th of February. I'm aware of this old topic however I cannot find (or use) any related information.
All I have is just parsed string to date - Date.parse '2020-02-10 8,00'
You are halfway there! Date.parse '2020-02-10 8,00' produces a ruby Date object, as you have noted. You now have to apply strftime. However strftime doesn't have any ordinalization so that piece has to be done manually.
date = Date.parse('2020-02-10 8,00')
date.strftime("%A, #{date.day.ordinalize} of %B") #=> Monday, 10th of February
the ordinalize method is provided by ActiveSupport.
If this format will be used multiple times in your app, you may wish to add an app-wide format:
# in config/initializers/time_formats.rb
Date::DATE_FORMATS(:ordinalized_day) = lambda{|date| date.strftime("%A, #{date.day.ordinalize} of %B")}
# anywhere in the app
Date.today.to_formatted_s(:ordinalized_day)

Retrieve Hash values with key in a specific date format

I'm using Rails. I've stored a count by month in a postgres db as a hash using hstore.
The stored hash is formatted as follows:
{"2017-03-01 00:00:00 UTC"=>"10", "2017-04-01 00:00:00 UTC"=>"3"}
I'm struggling to find a great way to retrieve specific month counts from this hash due to the date format used for the key.
QUESTION
What is the best way to format a string to match the current hash key date format?
For example for March in the Hash the key is "2017-03-01 00:00:00 UTC"
However, a new DateTime for March 1 2017 is formatted as "2017-03-01T00:00:00+00:00"
Or is it best to change the format of how I am storing the hash in the first place?
If you need a timestamp in a specific format, the standard tool to use is DateTime#strftime (all the time-ish classes will have a strftime method and they all behave the same). In your case:
some_datetime.utc.strftime('%Y-%m-%d %H:%M:%S %Z')
And hooking that up to ActiveRecord:
Model.where('your_hstore -> :key', :key => some_datetime.utc.strftime('%Y-%m-%d %H:%M:%S %Z'))
Or:
Model.where('your_hstore -> ?', some_datetime.utc.strftime('%Y-%m-%d %H:%M:%S %Z'))
%Z should be the "Time zone abbreviation name" and for me it produces strings like 'UTC', 'PDT', ... If your strftime (which almost certainly is just a wrapper around the system's libc version of strftime) doesn't produce the strings that you want then you have some options:
Drop the timezone completely if it will always be UTC. Then the keys would look like 2017-03-01 00:00:00 and you'd use '%Y-%m-%d %H:%M:%S' as your strftime format string.
If they keys are actually just dates as they appear to be, then use dates and drop the time-of-day. Then your keys would look like 2017-03-01, you'd use Date instances in Ruby rather than DateTimes, and you'd say some_date.strftime('%Y-%m-%d') or some_date.iso8601 in Ruby to get your hstore keys.
If you are using non-UTC timezones, then convert everything to UTC and go with 1 or 2.
If you don't want any of the above, switch to numeric timezone offsets (2017-05-10 18:05:57 +0000, 2017-05-10 18:06:48 +00:00, ...) and use %z, %:z, or %::z in the strftime format string (see the docs for difference between these three).
These of course require reworking any data you already have in the database but it is best to get the out of the way sooner rather than later.

How to use strptime to convert timestamp string with milliseconds to time object

I need to use strptime to convert a timestamp string with milliseconds to a Time object.
A work around is using parse:
t= Time.parse('29 Sep 2013 12:25:00.367')
=> 2013-09-29 12:25:00 -0400
But it is very important for my code to use strptime, because I want to be able to pass multiple types of format including: "HH:MM", "HH", etc. through the function.
I can do it with nanoseconds like this:
Time.strptime("12:34:56:789434", "%H:%M:%S:%N")
=> 2016-03-16 12:34:56 +0100
I want something like this:
Time.strptime("12:34:56:789", "%H:%M:%S:%[insert magic letter that represent milliseconds]")
My thought is that there must be a way to do it with milliseconds as well.
Is it possible and how?
Try %L.
Refer to Ruby's DateTime documentation.
If you can update to Ruby 1.9.3, it supports this using %3N:
http://ruby-doc.org/core-1.9.3/Time.html#method-i-strftime

Ruby: get TimeZone component of string

I'm working with Date strings in Ruby and want to determine if a string was passed with a timezone or not (beyond simply parsing the text). If no timezone is supplied, I want to convert it to a certain timezone dependent on other factors.
Example:
DateTime.parse("2014-01-01T23:59:00")
=> #<DateTime: 2014-01-01T23:59:00+00:00 ((2456659j,86340s,0n),+0s,2299161j)>
DateTime.parse("2014-01-01T23:59:00Z")
=> #<DateTime: 2014-01-01T23:59:00+00:00 ((2456659j,86340s,0n),+0s,2299161j)>
DateTime.parse("2014-01-01T23:59:00PST")
=> #<DateTime: 2014-01-01T23:59:00-08:00 ((2456660j,28740s,0n),-28800s,2299161j)>
The problem is that parsing "2014-01-01T23:59:00" and "2014-01-01T23:59:00Z" (with Zulu) yields the same result, when one is specifying "Zulu" and the other isn't. I'm sure the default behavior is to assume UTC if no zone is supplied.
To check that the date string doesn't end with a time zone, you can check that the minutes and seconds are the end of the string, using this regex: \d{2}:\d{2}$
Here are some examples using debuggex to illustrate:
\d{2}:\d{2}$
Debuggex Demo

Convert 2 types of date strings to datetime objects

I need a reliable way to convert formatted date strings into datetime objects so I can save into the database. I'm importing data from an RSS feed and the date strings look like this 10/31/2012 11:59:00 PM, but every once in a while one will come through with no time data, like this: 9/24/2012. Is there a way to convert the string to a datetime object regardless if the time is present or not?
I was using Date.strptime() because Date.parse() wasn't being reliable enough for me. Here's what I was using, which will error out when it encounters the date string without the time.
Date.strptime(i.xpath('activedate').text, '%m/%d/%Y %I:%M:%S %p').to_datetime
What would be the best way to handle this?
I recommend chronic:
require 'chronic'
Chronic.parse '10/31/2012 11:59:00 PM'
#=> 2012-10-31 23:59:00 0800
Chronic.parse '9/24/2012'
#=> 2012-09-24 12:00:00 0800
I'd just loop through an array of the possible date formats and try parsing until one succeeds:
parsed_date = nil
['%m/%d/%Y %I:%M:%S %p', '%m/%d/%Y'].each do |format|
parsed_date ||= DateTime.strptime(i.xpath('activedate').text, format) rescue nil
end

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