Today is international friendship day i.e. 2nd August. Earlier, on 27 July 2011 the 65th Session of the United Nations General Assembly declared 30 July as "International Day of Friendship". But nowadays it is celebrated on the first Sunday of August rather than 30 July.
A brief history thanks to Wikipedia:-
Friendship Day was originally promoted by Joyce Hall, the founder of Hallmark cards in 1930, intended to be 2 August and a day when people celebrated their friendships by sending cards. The second of August was chosen as the center of the largest lull between holiday celebrations. Friendship Day was promoted by the greeting card National Association during the 1920s but met with consumer resistance - given that it was too obviously a commercial gimmick to promote greetings cards. By the 1940s the number of Friendship Day cards available in the US had dwindled and the holiday largely died out there. There is no evidence to date for its uptake in Europe; however, it has been kept alive and revitalised in Asia, where several countries have adopted it.
In honor of Friendship Day in 1998, Nane Annan, wife of UN Secretary-General Kofi Annan, named Winnie the Pooh as the world's Ambassador of Friendship at the United Nations. The event was co-sponsored by the U.N. Department of Public Information and Disney Enterprises, and was co-hosted by Kathy Lee Gifford.
Some friends acknowledge each other with exchanges of gifts and cards on this day. Friendship bands are very popular in India, Nepal, Bangladesh and parts of South America. With the advent of social networking sites, Friendship Day is also being celebrated online. The commercialization of the Friendship Day celebrations has led to some dismissing it as a "marketing gimmick".
The intended purpose of celebrating days may be to promote a cause or an idea (World Environment Day is celebrated every year on 5 June); raise awareness (World AIDS Day, 1 December); romantic (Valentine day Feb 14); saving institution of marriage (Wife day is celebrated every year on the 2nd Sunday of the July month); family relations (mother’s day, father’s day) etc.
In a way it’s a very good idea. As they say every day is a friendship, valentine, husband, wife, mother, father etc day and there is no need to celebrate it on a particular given day. But It makes the person feel special for one day. So there is no harm. As such we pray daily and God is in our heart 27x7 but still we celebrate X-mas, Id, Holi, Diwali, Ram Navmi, Krishna Janamashtmi etc.
Some days or week are of Indian origin and they serve their purpose. Like we celebrate 14 Nov (Birthday of our first PM JL Nehru who loved children) as Children’s day.
We celebrate 14 Sept as Hindi Day as because on this day in 1949, the Constituent Assembly of India had adopted Hindi written in Devanagari script as the official language of the Republic of India. Hindi weeks or fortnights are celebrated in September and it raises awareness about using Hindi.
We celebrate pulse polio weeks, which is a UN initiative, throughout the year and it helped eradicate polio from India.
Recently our PM Narendra Modi celebrated 21 June as International Yoga Day. Hopefully it will increase soft power of India in the world.
So in a way there is no harm in celebrating days, weeks or months as long as these help to promote a cause.
Biggest criticism of these days is that these are marketing gimmicks of big corporations. This is true to some extent.
Secondly as there are so many days that even 365 days are not sufficient. So this becomes a self-defeating exercise as too much of everything is bad.
Sometime rowdy boys harass and stalk innocent girls, who are not interested in them, on days like valentine, rose, friendship etc. So it becomes misogynistic and ugly. On the other hand Hindu/ Muslim and other right wing activists oppose these on religious grounds and say these are against Indian culture. They harass publicly, genuine couples who are in love. This leads to very unpleasant situations and hooliganism.
Moreover relation centric days like mother, father, husband, wife etc is a poor idea in a sense that these can’t help much if we are morally and emotionally bankrupt. In some countries children don’t respect their parents and say that they are simply the byproduct of their lust. Similarly in the countries where divorce rate is too high days like husband/ wife can’t help much. These days becomes redundant and sham.