The TideSpy API uses some particular data types, which are described below:
Date and Time
Dates are typically in the form yyyymmdd, for example 20141203 for the 3 day of December, 2014.
Except for rare cases, dates and times are local times for the place in question, adjusted for daylight savings where appropriate.
Pros: You don't have to worry about your time zone, or daylight savings.
Cons: You can't make your own adjustments to the time without ambiguity, if daylight savings can occur.
Times come in a number of formats depending on the usage. In most cases they are local times for the place concerned, adjusted for daylight savings. Three formats are used in the API; HHMM is used to denote an hour (00-23) and minute of the day, HH:MM:SS denotes hour (00-23), minutes, and seconds, and sometimes just a minute of the day (0-1439) is used to simplify parsing and conversions.
Tide Turn
A tide turn is identified by a tide height, a time, and whether it is a high or low tide. A tide turn can be defined as the point at which the direction of the tide changes from incoming to outgoing or vice-versa. Because the rate of change of height near this point is very small, the time is difficult to measure and compute, however the height of the tide can be calculated quite precisely. A difference of perhaps ten minutes is of little consequence for all practical purposes, which is the market TideSpy is aimed at.
Tide Height
The height of a tide is important for, amongst other things, calculating the amount of water a boat has under its keel. It is defined as the water height above "chart datum", which is an absolute level defined by the country's authority in charge of tide information. Chart datums are the reference level used in official marine charts and allow users of water height information to calculate an actual water depth for any tide. TideSpy does not concern itself with datum information.
Please also remember that the heigh is a prediction and not a certainty. Winds and air pressure in particular can affect the tide height; the supplied values are derived from actual readings, so if, for instance, a particular place has a persistent onshore wind then the tide predictions may reflect that. They won't reflect the result of onshore winds from a hurricane!