# Problem with DateTime in query

**URL:** <https://www.ruby-forum.com/t/problem-with-datetime-in-query/150445>\
**Category:** Rails\
**Created:** [October 8, 2008, 5:37pm UTC](https://www.ruby-forum.com/t/problem-with-datetime-in-query/150445 "2008-10-08T17:37:17Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![cjharrelson](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/c89c15/32.png) [@cjharrelson](https://www.ruby-forum.com/u/cjharrelson)\
**Post date:** [October 8, 2008, 5:37pm UTC](https://www.ruby-forum.com/t/problem-with-datetime-in-query/150445/1 "2008-10-08T17:37:17Z")

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Here is a strange one for you:

I am using rails 2.1.0. I am also using the Time zones feature.

I have a User model that has many enrollments. The Enrollments model  
has several named scopes, one of which is today:

# This named scope is adjusted to UTC

named\_scope :today, :conditions =\> [“updated\_at \>= ? AND updated\_at  
\<= ?”,  
Time.zone.now.beginning\_of\_day.utc, Time.zone.now.end\_of\_day.utc]

If I start the server and use user.enrollments.today, I get back  
today’s enrollments, as you would expect. Once tomorrow arrives, and  
I utilize the same query, I get yesterday’s enrollments. I have put  
the server’s logger in debug mode to capture the queries and sure  
enough, it is asking for yesterday’s enrollments.

First day’s log:

Processing CoursesController#show (for 66.249.102.37 at 2008-10-07  
13:24:35) [GET]  
…  
maxed\_out\_hours\_for\_today?() begin  
calculate\_hours\_today() begin  
hours\_today: 0.0  
[4;36;1mEnrollment Load (0.001272) [0m [0;1mSELECT \* FROM  
`enrollments` WHERE (`enrollments`.user\_id = 213) AND (((updated\_at \>=  
‘2008-10-07 04:00:00’ AND updated\_at \<= ‘2008-10-08 03:59:59’) AND  
(mode = ‘evaluated’)) AND (exam\_id IS NULL)) [0m  
Found 6 enrollments for user \*\*\*\*\*\*\*\*\*\*

Second day’s log:

Processing CoursesController#show (for 66.249.102.37 at 2008-10-08  
07:22:19) [GET]  
…  
[4;35;1mEnrollment Load (0.001750) [0m [0mSELECT \* FROM  
`enrollments` WHERE (`enrollments`.user\_id = 213) AND (((updated\_at \>=  
‘2008-10-07 04:00:00’ AND updated\_at \<= ‘2008-10-08 03:59:59’) AND  
(mode = ‘evaluated’)) AND (exam\_id IS NULL)) [0m  
Found 6 enrollments for user \*\*\*\*\*\*\*\*\*\*\*\*\*

Notice that the dates are the same on both days. This makes no sense  
because Time.zone.now.beginning\_of\_day.utc and  
Time.zone.now.end\_of\_day.utc are what is being used in teh  
named\_scope. It does not seem to be a time zone issue, as we are in  
CDT, which is -5 from UTC right now. The second day’s query is  
outside of the possible 5 hour overlap if I was making a mistake.

Does anyone have any idea what could be causing this?

---

<div class="post-metadata">

**Author:** ![cjharrelson](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/c89c15/32.png) [@cjharrelson](https://www.ruby-forum.com/u/cjharrelson)\
**Post date:** [October 8, 2008, 5:56pm UTC](https://www.ruby-forum.com/t/problem-with-datetime-in-query/150445/2 "2008-10-08T17:56:01Z")

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On 8 Oct 2008, at 16:36, cjharrelson wrote:

> \<= ?",  
> Time.zone.now.beginning\_of\_day.utc, Time.zone.now.end\_of\_day.utc]

The Time.zone.now is evaluated precisely once: when the model is  
loaded. Use a lambda (see the section on procedural scopes in the api  
docs) to do something like

named\_scope :today, lambda { :conditions =\> stuff here is evaluated  
each time the scope is accessed }

Fred

---

<div class="post-metadata">

**Author:** ![cjharrelson](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/c89c15/32.png) [@cjharrelson](https://www.ruby-forum.com/u/cjharrelson)\
**Post date:** [October 8, 2008, 7:07pm UTC](https://www.ruby-forum.com/t/problem-with-datetime-in-query/150445/3 "2008-10-08T19:07:01Z")

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Ryan B.’ screencast on this topic -

> **[\#108 named\_scope - RailsCasts](http://railscasts.com/episodes/108-named-scope)**
>
> Short Ruby on Rails screencasts containing tips, tricks and tutorials. Great for both novice and experienced web developers.

- has more details about delaying evaluation of the condition with a  
lambda (including optional argument).

How weird, I literally just watched his screencast before reading this  
question.

On Oct 8, 8:54 am, Frederick C. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)