Time Conversion Between Ruby on Rails and JavaScript Vice Versa

Time conversion between ruby on rails and javascript vice versa?

Perhaps the most reliable way is to use seconds since the epoch for ruby, and milliseconds for JavaScript.

In ruby:

t = Time.now
# => 2014-03-12 11:18:29 -0700
t.to_f * 1000 # convert to milliseconds since 1970-01-01 00:00:00 UTC.
# => 1394648309130.185

This value can be directly given to the JavaScript Date constructor:

var d = new Date(1394648309130.185)
d // Wed Mar 12 2014 11:18:29 GMT-0700 (Pacific Daylight Time)

d.getTime() // 1394648309130 (Fractions of a millisecond are dropped)

The output of d.getTime() divided by 1000 can be given to ruby's Time.at():

Time.at( 1394648309130 / 1000.0 )
# => 2014-03-12 11:18:29 -0700

How to parse date with time zone from a custom string?

Normally JS new Date returns like this.

(new Date).toString(); // => "Fri Oct 30 2015 00:36:43 GMT+0900 (JST)"

I guess your JS datetime string is missing + after GMT.
This works perfectly

'Thu Oct 29 2015 15:46:19 GMT+0100 (CET)'.to_datetime # => Thu, 29 Oct 2015 15:46:19 +0100

Calculate time from an array and convert to time zone

You have to calculate the average on the gap from midnight.

A not elegant (but fast) solution could be:

# Keep only time    
bed_times.map! { |bt| Time.parse(bt.split(" ")[1]) }

# calculate the gap from 00:00:00
gap_from_midnight = bed_times.map do |bt|
  if bt > Time.parse("12:00:00")
    gap = (bt.to_f - Time.parse("24:00:00").to_f)
  else
    gap = (bt.to_f - Time.parse("00:00:00").to_f)
  end
  gap.to_i
end

# average in sec
avg_in_sec = gap_from_midnight.inject(:+) / bed_times.size

# average in UTC time zone 
avg = Time.at(avg_in_sec).utc # => 1970-01-01 05:26:57 UTC (result for bed_times array)

# average in PST time zone (see note)
avg_pst = Time.parse(avg.to_s).in_time_zone("Pacific Time (US & Canada)") # => Wed, 31 Dec 1969 21:26:57 PST -08:00 (result for bed_times array)

# Keep only time
avg_pst.strftime("%H:%M:%S") # => "21:26:57" (result for bed_times array)

With your bed_times array (with the values as a string)

bed_times = [
  "2015-12-10 05:58:24 UTC",
  "2015-12-09 03:35:28 UTC",
  "2015-12-08 06:32:26 UTC",
  "2015-12-07 01:43:28 UTC",
  "2015-12-05 07:49:30 UTC",
  "2015-12-04 07:02:30 UTC"
]

the average is :

• 05:26:57 in UTC zone
• 21:26:57 in PST zone

With another array like this

bed_times = [
  "2015-12-10 01:00:00 UTC",
  "2015-12-09 23:00:00 UTC",
  "2015-10-19 18:00:00 UTC",
]

the average is:

• 22:00:00 in UTC zone
• 14:00:00 in PST zone

note: .in_time_zone is a helper from ActiveSupport::TimeWithZone
http://api.rubyonrails.org/classes/ActiveSupport/TimeWithZone.html

Ruby/Rails - Convert Unix Timestamp to HH:MM am/pm with Timezone

You have basically two alternatives:

1. server-side approach
2. client-side approach using JavaScript

I explained both in this answer no more than a few days ago.

How to convert BSON::Timestamp to ruby time and vice versa

You can convert a BSON::Timestamp to a BSON::ByteBuffer using the #to_bson method.

You can then convert the BSON::ByteBuffer to an integer (#get_int64) that represents the number of milliseconds since the epoch.

Then use Time::at to convert that integer to a Time object

date_time = DateTime.new(2021,8,30)
date_time.to_time
#=> 2021-08-30 00:00:00 +0000
date_time.to_time.to_i
#=> 1630281600 
timestamp = BSON::Timestamp.from_bson(date_time.to_bson)
#=> #<BSON::Timestamp:0x00007fffe31da4a8 @seconds=379, @increment=2488994816>
timestamp.to_bson.get_int64 / 1000 
#=> 1630281600
Time.at(timestamp.to_bson.get_int64 / 1000).utc
#=> 2021-08-30 00:00:00 UTC

convert time DD:hh:mm:ss format into seconds in Rails 3

You didn't state which version of ruby you were using, so I'm assuming something modern. This should work on 1.9.3 or later. This also assumes that you always have all 4 fields present. It should give you some ideas anyway.

> db_value = '456:14:56:10'
=> "456:14:56:10"
> units = %w{days hours minutes seconds}
=> ["days", "hours", "minutes", "seconds"]
> db_value.split(":").map.with_index{|x,i| x.to_i.send(units[i])}.reduce(:+).to_i
=> 39452170

How to convert a unix timestamp (seconds since epoch) to Ruby DateTime?

DateTime.strptime can handle seconds since epoch. The number must be converted to a string:

require 'date'
DateTime.strptime("1318996912",'%s')

Collecting and converting date field for an array

Todo.all.map { |todo| todo.date.strftime("%m/%d/%y") }

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