Under time charterparty the owner let his vessel to the charterer for a period of time, therefore when compared with single voyage or with series of single geographical voyages under the voyage charter contracts, time charter instead of provisions for freight, laytime and demurrage has stipulations for payment of hire, delivery, redelivery and off-hire events.
Per Popplewell J in The Wisdom C  EWHC 1884 (Comm) at para 30.
This is as true of a trip time charter, such as the charterparty in this case, as of a term time charter. Although the length of the period of hire is limited by a trip defined within a geographical range (and sometimes, though not in this case, by a maximum duration), the nature of the contract for the duration of the period remains that of making the vessel and her crew available to the charterers as a means for the charterers to transport goods, not a contract for carriage of the goods by the owners.
Per Sir Bernard Eder in SBT Star Bulk & Tankers (Germany) GmbH & Co KG v Cosmotrade SA  EWHC 583 (Comm) at paras.12-13:
11. For present purposes, it is sufficient to note that from the charterer’s perspective one of the advantages which a time charter (including a time trip time charter) has over a voyage charter is that voyage orders under a time charter do not constitute an irrevocable election: see, for example, the comments of Donaldson J in The Aragon  1 Lloyd’s Rep 628 at p633 lhc where he stated that it was "wholly foreign to the whole conception of a time charter-party, which entitle[s] the charterer upon paying the hire to call upon the vessel to visit any port or ports which he wishe[s] within trading limits subject to any express agreement to the contrary".
12. For my part, I think that it is also important to recognise that the concept of a "trip time charter" embraces (or at least may embrace) a number of possible permutations. For example, a "trip" may involve loading cargo at A and a single voyage to X to discharge the cargo there i.e. at X. Alternatively, it may involve loading cargo at a number of different ports e.g. A, B and C and a voyage to X to discharge the cargo there or perhaps at a number of different discharging ports e.g. X, Y and Z. Alternatively, it may involve several loading and discharging operations at different ports along a route from A to Z e.g. loading at A discharging at X, then loading at B discharging at Y and then loading at C discharging at Z. As a matter of language, I think that these examples might all be described as involving a single "trip". In my view, there is no single definition as to what constitutes a "trip" or "one trip".
13. Ultimately, the scope of any "trip time charter" will depend upon the particular terms agreed between the parties. However, I accept the basic underlying notion of any time charter including a trip time charter viz. that the vessel will generally be under the directions and orders of the charterer as regards her employment for the charter period. Of course, the charterers' entitlement to give directions and orders may be restricted by whatever may be agreed between the parties with regard, for example, to period, trading limits, geographical route and even (perhaps) number and designation of loading and discharging ports or ranges. However, any such restriction would have to be specifically agreed and, in my view, would require clear words.