Hi @Turulense2020 ,
Could you please share a bit more about the whole configuration of your second flow?
Could you please show more details about the date variable displayed in your canvas app? Is it displayed in proper date format value as that in your Excel table?
Based on the issue that you mentioned, I think this issue may be related to time zone. Firstly, please make sure the "Regional format" option is set to your locale value:

In addition, when working date time value in Power Automate flow, it would be converted into UTC format automatically. In other words, when you pass the "03/28/2020" date value from your canvas app into your flow, the "03/28/2020" date value would be converted into corresponding UTC Format value automatically, so when you reference the date value in your flow, it would be the UTC format of the passed date value from app.
As an fixed solution, I think the "Convert time zone" action could achieve your needs. You should configure your second flow as below:

If you want to populate the received date value into your SP list through the "Create item" action in your second flow, please make sure your SP Site Time Zone is also set to your local time zone value as below:

Best regards,