data reconciliation between Email Insights report and API data

Data_Analytics
Level 1

data reconciliation between Email Insights report and API data

I have extracted activity data via Marketo API. Now I am reconciling my email sent data between Marketo Email Insights report on Marketo portal and my extracted data. I selected custom date range (1st Apr 19 to 30th Apr 19) on Email Insights dashboard on Marketo portal and download the excel report. And then compare it with my extract activity data for period (activity date: 1st Apr 19 to 30th Apr 19). However, I found some small difference for most of the emails. I guess it may be caused by time zone difference. Can you please clarify what is the time zone on Email Insights on Marketo Portal? What is the time zone of activityDate of activity data through API ?