CODEWITHSUNDEEP
ruby-on-railsrubystrptime
bokeken3
bokeken3

Reputation: 23

Parsing date using strftime

I have a problem parsing dates taken in from scraping a website using Nokogiri. I scrape the datetime using 

@date = h4.at('time[itemprop="startDate"]')[:datetime]

This gives me 2015-04-28 19:30:00 UTC, which is inserted into my date column, of type "datetime".

Using strptime I am trying to parse the date into a "dd/mm" format, and enter it into my Rails table:

Date.strptime(@date, "%Y-%m-%d %H:%M:%S %Z").strftime("%m/%d/%Y")

@event=Event.new
@event.date= @date

Any help would be very much appreciated.

Upvotes: 2

Views: 3320

Answers (2)

the Tin Man
the Tin Man

Reputation: 160571

Here's some code that might help:

require 'date'
require 'time'

date = Date.strptime('2015-04-28 19:30:00 UTC', "%Y-%m-%d %H:%M:%S %Z")
# => #<Date: 2015-04-28 ((2457141j,0s,0n),+0s,2299161j)>
date.strftime('%m/%d/%y')
# => "04/28/15"

Parsing into a Date object stores only the year, month and day information.

datetime = DateTime.strptime('2015-04-28 19:30:00 UTC', "%Y-%m-%d %H:%M:%S %Z")
# => #<DateTime: 2015-04-28T19:30:00+00:00 ((2457141j,70200s,0n),+0s,2299161j)>
datetime.strftime('%m/%d/%y')
# => "04/28/15"

time = Time.strptime('2015-04-28 19:30:00 UTC', "%Y-%m-%d %H:%M:%S %Z")
# => 2015-04-28 19:30:00 UTC
time.strftime('%m/%d/%y')
# => "04/28/15"

Parsing into a DateTime, or Time object captures all the information.

The error you're seeing is often caused by a date string in a format you don't expect. That often happens when you expect a value in 'mm/dd/yy' order, but actually receive one in 'dd/mm/yy' order. This happens because the US uses 'mm/dd/yy' and most of the rest of the world uses 'dd/mm/yy':

date = Date.strptime('2015-28-04', '%Y-%m-%d')
# ~> -:7:in `strptime': invalid date (ArgumentError)

or

date = Date.strptime('28-04-2015', '%m-%d-%Y')
# ~> -:7:in `strptime': invalid date (ArgumentError)

You can work around that by using some rescue statements to try several different formats.

You don't want to use parse because it'll assume 'dd/mm/yyyy' and will blow up with US dates, and is slower because it tries multiple formats before giving up. So, using fixed formats you expect is the way to go but you need to search for your various formats of date/datetime strings you'll expect to find and write format strings to match. And, since you're scraping pages, it's possible to find a LOT of bad/malformed values so program defensively.

Upvotes: 2

infused
infused

Reputation: 24337

You don't need strftime and you can parse the date with parse. Just convert the string to a Date object and assign that to your ActiveRecord attribute:

@event = Event.new
@event.date = Date.parse('2015-04-28 19:30:00 UTC')

Upvotes: 0

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