SQL Query to select the date of switching

I have a question. i have a table containing 4 columns.

uid date version type 1 03-02-2015 1.1 windows 1 05-02-2015 1.1 ubuntu 1 07-02-2015 1.1 android 2 03-02-2015 1.1 windows 2 05-02-2015 1.1 ubuntu 2 07-02-2015 1.1 android

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In that i need to write sql query to select the date when the user changed from window to ubuntu. Please help me how to write this?