AWS Cost and Usage Reports (CUR) with the "Overwrite Existing Report" option and Report data time granularity "Daily"

Your understanding is partially correct, but let me clarify a few points about how AWS Cost and Usage Reports (CUR) work with the "Overwrite Existing Report" option and "Daily" time granularity.

With the "Overwrite Existing Report" option, AWS uses a specific folder structure in your S3 bucket. Based on your provided bucket name and folder structure, it would look like this:

finops-devtestv2/test-CUR/test-finops/yyyymmdd-yyyymmdd/test-finops-00001.csv.zip

For the data of January 2, 2025, you would indeed be looking in the folder for the current month, which is 20250101-20250201. However, it's important to note a few things:

1. The report is updated at least once a day, but it's cumulative for the month. This means that the report will contain data from January 1 up to the most recent update on January 2.

2. The data you see is not real-time. There can be a delay of up to 24 hours for the data to appear in the report.

3. If you check at the 23rd hour of January 2, 2025, you will likely see data for January 1 and most of January 2, but it may not include the full 24 hours of January 2 due to the processing delay.

4. The charges shown in the report throughout the month are estimates and subject to change as you continue to use AWS services.

5. AWS finalizes the report's usage charges after issuing an invoice at the end of the month.

So, while you will see a folder for 20250101-20250201 and it will contain data for January 2 when you check on that day, it may not be the complete data for the full 24 hours of January 2 if you check at the 23rd hour. For the most accurate and complete data, it's best to wait until the following day or even a few days into the next month when the report for the previous month is finalized.
Sources
What are AWS Cost and Usage Reports? - AWS Data Exports
Understanding your report versions - AWS Data Exports
Creating reports - AWS Data Exports