 # Subtract time

Hey everyone

``````        i am trying to subtract two different times.i am getting right when i have two fixed times.
``````

here is my code

def hour_min(last,first)

``````difference = last - first
seconds    =  difference % 60
difference = (difference - seconds) / 60
minutes    =  difference % 60
difference = (difference - minutes) / 60
hours      =  difference % 24

return hours,minutes
``````

end
if last =9:30 PM and first = 10:52 i get after subtraction 10 hours : 38 mins but the problem is with Time.now
if last = Time.now and first = 10:30 am it is give improper output

this is my view
<% hour_min = hour_min(Time.now.to_i,cin.first.to_i)%>
<%="#{hour_min}Hour : #{hour_min}Min"%>

My problem is if i have two fixed timings i am getting correct but when i have to calculate with Time.now i am getting wrong answer can any one help me out

Cheers

Hey everyone

i am trying to subtract two different times.i am getting right
when i have two fixed times.
here is my code

def hour_min(last,first)

difference = last - first
seconds = difference % 60
difference = (difference - seconds) / 60
minutes = difference % 60
difference = (difference - minutes) / 60
hours = difference % 24

return hours,minutes

end
if last =9:30 PM and first = 10:52 i get after subtraction 10 hours : 38
mins but the problem is with Time.now
if last = Time.now and first = 10:30 am it is give improper output

this is my view
<% hour_min = hour_min(Time.now.to_i,cin.first.to_i)%>

You should not need to call to_i, just pass in the times, the
difference of two times is the difference in seconds.

<%="#{hour_min}Hour : #{hour_min}Min"%>

My problem is if i have two fixed timings i am getting correct but when i
have to calculate with Time.now i am getting wrong answer can any one help
me out

Have a look at the Rails Guide on debugging which will show you
techniques that can be used to debug the code. I would start just by
running the console (rails c) and try calling your method with various
values and see what happens. You can use puts in the method to print
intermediate results and see what is happening.

What results are you getting? Is it a number of hours out? If so
then I guess it is a time zone issue.

Colin

@colin if i have two timings9:30 PM and 10:52 i got correct output here it is 10 hours : 38mins
and if i give Time.now as one input and 10:30 AM as another input i got 2 hours : mins

i dont think it is timezone issue because if there are two fixed inputs and if i subtract them with my code i get the correct output the only issue is with Time.now as a input i guess. i wanna calculate the working hours with mins of an employee. As i explained before if the employee checkin and checkout time is there i can able to calculate it and if i wanna show right from his checkin until he checkout every min of his working hours and mins i have to go for Time.now as another input.

Hey everyone

``````        i am trying to subtract two different times.i am getting right
``````

when i have two fixed times.

here is my code

def hour_min(last,first)

``````difference = last - first
``````
``````seconds    =  difference % 60
``````
``````difference = (difference - seconds) / 60
``````
``````minutes    =  difference % 60
``````
``````difference = (difference - minutes) / 60
``````
``````hours      =  difference % 24
``````
``````return hours,minutes
``````

end

if last =9:30 PM and first = 10:52 i get after subtraction 10 hours : 38

mins but the problem is with Time.now

if last = Time.now and first = 10:30 am it is give improper output

this is my view

<% hour_min = hour_min(Time.now.to_i,cin.first.to_i)%>

You should not need to call to_i, just pass in the times, the

difference of two times is the difference in seconds.

If i don’t call with to_i the output will be with decimal(i.e., 3.o hours ) to convert them i went with to_i

@colin if i have two timings9:30 PM and 10:52 i got correct output here it
is 10 hours : 38mins
and if i give Time.now as one input and 10:30 AM as another input i got 2
hours : mins

The best thing is to put in some diagnostic code and work out what is
happening. Remember Time.now is not a time of day it is a date and
time. Hopefully your other times are also full date and time objects.

Colin

@colin here i found in console

@bio = Biometric.find(36457)
=> #<Biometric id: 36457, rfid: 0, userid: 3, date_time: “2012-08-29 09:30:00”, checkin_checkout: nil, forget: nil, reason: nil, entered_by: nil, created_at: “2012-08-29 09:30:00”, updated_at: “2012-08-29 09:30:00”, RealCheckIn: nil, MACHINENO: nil>

@first = @bio.date_time.to_i
=> 1346232600

@now = Time.now
=> Wed Aug 29 12:13:46 +0530 2012

@time_now = @now.to_i
=> 1346222626

@time_now - @first
=> -9974

@first = @bio.date_time
=> Wed, 29 Aug 2012 09:30:00 UTC +00:00
with out converting to to_i

@now = Time.now
=> Wed Aug 29 12:16:48 +0530 2012
with out converting to_i

as i found was my date from database is in UTC format and when it comes to Time.now its not UTC

how can i solve it

Cheers

@colin here i found in console

@bio = Biometric.find(36457)

=> #<Biometric id: 36457, rfid: 0, userid: 3, date_time: "2012-08-29
09:30:00", checkin_checkout: nil, forget: nil, reason: nil, entered_by: nil,
created_at: "2012-08-29 09:30:00", updated_at: "2012-08-29 09:30:00",
RealCheckIn: nil, MACHINENO: nil>

@first = @bio.date_time.to_i

=> 1346232600

@now = Time.now

=> Wed Aug 29 12:13:46 +0530 2012

@time_now = @now.to_i

=> 1346222626

@time_now - @first

=> -9974

@first = @bio.date_time
=> Wed, 29 Aug 2012 09:30:00 UTC +00:00
with out converting to to_i

@now = Time.now

=> Wed Aug 29 12:16:48 +0530 2012
with out converting to_i

as i found was my date from database is in UTC format and when it comes to
Time.now its not UTC

how can i solve it

First a slight correction. The time in the database is not in UTC
/format/ it is just in UTC. UTC is not a time format it is a time
zone. Assuming that the column type is datetime (look in db/schema.db
to check) it should not be a problem. When you subtract the times it
should allow for the different time zones and give you the correct
difference in seconds, provided that the time in the database is
correct for UTC. If that is not working for you please give an
example of it not working.

If it makes it easier for you to understand what is going on you can
convert Time.now to utc by using Time.now.utc. That will not change
the result when you subtract the utc time in the database of course,
as it is still the same time, just represented in a different time
zone.

Colin

You can do

(Time.now - Time.mktime(*ParseDate.parsedate((t.created_at).to_s)))

You can do

@swathi thanks for your reply but, i did not get ur trying to say. what is that Time.mktime and y u want o convert it to string

@swathi thanks i got what i need

Cheers

i got the answer what i am expecting but can u explain me

(Time.now - Time.mktime(*ParseDate.parsedate((t.created_at).to_s)))
what exactly this line does" Time.mktime(*ParseDate.parsedate((t.created_at).to_s)) "

You can do

(Time.now - Time.mktime(*ParseDate.parsedate((t.created_at).to_s)))

But why would you do that?

Colin