Our data for Ontario might seem different from other sources - here's why.
The Province of Ontario reports their data daily at 8:30CST; however this data is actually from the previous day at 14:00CST when it is extracted from their provincial reporting system. As such, the values reported by the province are nearly a full day out-of-date by the time they are released.
In order to better represent the current situation, data is collected from the individual Public Health Units (PHUs) in Ontario which report throughout the day.
This is consistent with what is considered by the Province of Ontario to be more accurate and more up-to-date than what they release daily. This can be seen in the footnotes of their data table, stating "In the event of a discrepancy between iPHIS cases and cases publicly reported by PHUs, data reported by PHUs should be considered the most up to date."
These changes were retroactively applied to April 1st through April 3rd, using open data from the COVID-19 Canada Open Data Working Group. As a result, a rather large spike in Ontario cases is seen on April 1st; this is not an accurate representation of the case changes on April 1st but was neccesary in order to back-fill cases reported by PHUs but not by the provincial government.
Now, cases are added in near real-time to the Ontario total throughout the day as each of the Public Health Units report in. As such, you may notice the number increasing until the last PHU reports in the late afternoon.
If you have any additional questions about this change, please feel free to reach out.