|- summer (DST)||CEST (UTC+2)|
Haslev is popularly known as the school town with the green surroundings (skolebyen i det grønne). There are no less than six public schools, two boarding schools, a folk high school, and a technical school - as well as a college of education and a sixth-form college.
Haslev started out being a small village named Hasle with a few houses and streets around the church. The name was changed to Haslev to avoid confusion with other similar town names in Denmark.
In 1870, the railway line passing Haslev town was inaugurated. At that time, Haslev had only 653 inhabitants. A street named Jernbanegade (Railway Street) was paved, to connect the church with the newly built train station. In the years that followed, the street became the main street of the town with shops, banks and so forth. In 1911, the town had 3,668 inhabitants. In the 1980s, a square in the middle of the street was constructed.
During the 20th century Haslev grew rapidly, becoming a center for the Church Association for the Inner Mission in Denmark. The latter built a folk high school, sixth-form college (with a boarding school) among others. In the 1970s and 1980s, the schools became independent of the founding association. Today, there are only few remains of the Inner Mission in Haslev.
In the early 1970s and onwards, an entrepreneur named Ole Christiansen founded whole new neighbourhoods of one-family houses with an attached garden at a low expense. This encouraged many families from all over Zealand, and especially Copenhagen, to move to Haslev.
Prior to 1 January 2007, Haslev was a town in Haslev Municipality (kommune). On 1 January 2007 Haslev as the result of Kommunalreformen ("The Municipal Reform" of 2007), became a town in Faxe municipality.
- Emilie Ulrich (1872 in Frerslev – 1952) a Danish soprano who sang leading roles at the Royal Danish Opera from 1894 until 1917
- Jesper Bodilsen (born 1970 in Haslev) a Danish jazz double bassist
- Anders Egholm (born 1983 in Haslev) a Danish professional football defender, who plays for SønderjyskE
- Haslev Sixth Form College (Haslev Gymnasium & HF)
- Haslev College of Education (Haslev Seminarium)
- The folk high school (Haslev Udvidede Hoejskole)