Difference in Date properties (Modified vs Modified.) from Rest API

What type of issue is this?

Documentation issue / typo

What SharePoint development model, framework, SDK or API is this about?

SharePoint REST API

Target SharePoint environment

SharePoint Online

What browser(s) / client(s) have you tested

• [X] 💥 Internet Explorer
• [X] 💥 Microsoft Edge
• [X] 💥 Google Chrome
• [X] 💥 FireFox
• [X] 💥 Safari
• [ ] mobile (iOS/iPadOS)
• [ ] mobile (Android)
• [ ] not applicable
• [ ] other (enter in the "Additional environment details" area below)

Additional environment details

• browser version
• SPFx version
• Node.js version
• etc

Issue description

Recently we were investigating Date issue in our custom extension. We found that there are two different date formats coming for same property, for example: Modified: 10.03.2022 and Modified.: 2022-03.22T09:08

We couldn't find any documentation regarding second property with . at the end. What such properties means actually? can we rely on these properties in our custom applications?

Can anyone please share your ideas here.

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