OU's site (citing Rambam Berakhot 8:4) says that by default you should say shehakol, unless certain conditions are met:
Shehakol is recited over the honey of dates. Nevertheless, if one crushes dates manually, removes the pits and makes them into a dough-like substance, the bracha is Borei pri ho’eitz beforehand and the bracha that includes the three themes of bentching (i.e., al ho’eitz) after.
This ruling is based on Berakhot 38a:
.ואמר מר בר רב אשי האי דובשא דתמרי מברכין עלויה שהכל נהיה בדברו. מ"ט זיעה בעלמא הוא
Mar son of R. Ashi also said: Over honey of the date-palm we say, 'by whose word all things exist'. What is the reason? — Because it is merely moisture [of the tree]. Soncino translation
Based on this argument it can be said that the berakha achrona is borei nefashot. However, this view was later contested by בה"ג, as it is discussed in this article (see also Pesachim 24b on the other hand). In contrast, Rambam's ruling was confirmed in Orach Chayim 202:8.