In a current project we are using Solr for the first time. We ran into several problems which all of you may had. Most of them are well documented and a solution is easy to find. This blog post describes an issue with non UTC dates which was not that easy to find.
My use case was to build a news application where each item has a field
Publication Date. The date is stored in Solr as follow (in UTC):
"publication_date_tdt" : "2016-09-15T00:00:00Z"
Now when I want to query all news that are older than first of January 2016, I first need to get the date:
var myDate = new DateTime(2016, 1, 1);
Depending on your current culture this date won't be in UTC. When using this date now in your Solr query, your search log will have the following entry in it:
Your query is using non UTC dates. field:publication_date_tdt value: 01.01.2016 00:00:00. You will probably have incorrect search result.
By default, Sitecore/Solr recalculates the date to be in UTC. In my current case, the date which will be queried will be
31.12.2016 22:00:00 which will return incorrect results. The easiest solution is to get your date in UTC and use this in your Solr query instead. You can convert your date into a UTC date (without chaning the actual time) with the following code snipped:
var myUtcDate = DateTime.SpecifyKind(myDate, DateTimeKind.Utc);
This is very simple, but is also a bit risky. In my specific case this works as it is exactly what I want. But you should always care about timezones and be sure that you query your index or database in the correct timezone and with the correct dates. I hope that helps the next one who searches for this error message and didn't find a solution ;-)