Impression: if a person saw the ad on Jan 1st but converted on Jan 2nd, you see a conversion on Jan 1st.
Conversion: if a person saw the ad on Jan 1st but converted on Jan 2nd, you see a conversion on Jan 2nd.
Mixed: actions that occur on your ad (such as impressions and link clicks) will be reported under impression time, and actions that occur off your ad (such as a purchase on your website) will be reported under conversion time.