I'm actually a little late in acknowledging this but last Tuesday (17 May) was Vesak Day which meant a public holiday in Singapore. More about what I did with my day shortly.
One thing I've noticed since moving to Singapore, particularly where we live but I assume all over the island, is that whenever there is a religious holiday marquees etc. appear almost overnight with temporary stalls and stands etc. for people celebrating to congregate and enjoy the festivities together. Near where I live is a large expanse of grass and a marquee was quickly erected. This also happened last year during Ramadan and for the celebrations following the period of fasting (and I assume will happen again this year). Therefore about a week before a huge marquee was erected, flags put up etc. and I noticed at another similar site nearby a huge Buddha appeared as well. So regardless of whether you realised beforehand this would ensure you quickly realised something was happening soon. Although I should add that I did know Vesak day was approaching.
I'll be honest though in that I did not know what Vesak day was in celebration of. So for those of you who may be as equally unsure as I was in a very brief nutshell Vesak day is traditionally celebrated by Buddhists and is the most significant day in their religious calendar. It is also sometimes know as Buddha's birthday but the day actually celebrates the birth, enlightenment and death of Buddha. The date for the day can vary but it usually falls within May.
There is a wealth of information regarding this day and its significance for Buddhists which can be read. If you are interested in finding out more about Vesak day specifically in Singapore I would suggest taking a look at this website as a starting point.