SQLite strftime function issue with timezone

I have following table structure where are saved some dates:

I tried to group results by hours using strftime sqlite function, but i found the problem if datetime value is stored like:

2015-01-21 11:49:16CET

In this case is value not converted. But if i erased "CET" value to have something like this:

2015-01-21 10:44:09

I got the correct result.

Query:

SELECT strftime('%H', dc.date) as hr,
       COUNT(*) AS DIALS_CNT,
       SUM(CASE WHEN dc.call_result = 'APPT' THEN 1 ELSE 0 END) AS APPT_CNT,
       SUM(CASE WHEN dc.call_result = 'CONV_NO_APPT' THEN 1 ELSE 0 END) AS CONVERS_CNT,
       SUM(CASE WHEN dc.call_result = 'CANNOT_REACH' THEN 1 ELSE 0 END) AS CANNOT_REACH_CNT
FROM dialed_calls dc
GROUP BY strftime('%H', dc.date);

Should i remove timezone from date column or how can i solve it please?

Many thanks for any advice.