@Odd Job
Unfortunately the authority MSA does not provide such info. New notes are usually released around December or early January in readiness for the Chinese New Year demand. In Singapore/Malaysia, they used to open up new teller counters for customers to get new UNC banknotes for the Chinese New Year. I am not sure if they still do that, as a couple of years ago (during Covid), the government in Singapore encouraged the people to use circulated notes that are still in great condition.
Of course, MAS also released new banknotes as and when required, like before Ramadan and when there is a public demand for it. To find out when a particular note was released, this is all relying on sightings by collectors or dealers in Singapore. Below is the list I have for my records:
$2 - Goh Chok Tong
2006 - no symbol
2009? - solid square
2009 - 2-soild square
2011 - triangle
2011 - 2-triangle
$2 - Tharma Shanmugaratnam
2013 - diamond
2015 - 2-diamond
2016 - solid star
2017 - 2-hollow star, hollow star, 2-solid star
2018 - 3-soild star
2019 - 3-hollow star
2019 - solid house
2020 - 2-solid house
2023 - 3-solid house
2024 - inverted triangle
If you have all in your collection, you have done well. I am still missing the 2024 prints.