A candidate whose role changed in their 5th year from NOC 10022 (Advertising Manager) to NOC 21233 (Web Designer) — without a computer science degree, but with duties matching the new NOC — asked which date to record for the "date started" field when using the newer NOC as their primary occupation.
According to the thread: for most occupations (outside of regulated trades), you can use your university graduation date as the start date, rather than the exact date your duties shifted to the new NOC. The exception is trade occupations, where the start date usually needs to reflect when you obtained the required certification, since those roles can't legally be practiced without it.
The thread didn't fully resolve whether a mismatch between your NOC and your educational background (no computer science degree, but web-design duties) creates a separate issue — that part of the question needs independent verification, since a reference letter matching duties to the NOC is generally what matters most, not your degree field, but confirm this against current IRCC guidance for your specific NOC before relying on it.