Because chains are noisy and expensive to manufacture, timing belts have phased them out.  It's best to replace your Daihatsu timing belt at the time recommended in your owner's manual.  Typically, that time will be anywhere between 60,000 and 105,000 miles.  Your timing belt works by turning the camshaft(s) at precisely ½ the speed of the crankshaft and maintains a precise alignment.  The two types of engines that use timing belts are interference engine and non-interference engines.  If the timing belt slips on an interference engine, the piston can collide with an open valve and cause it to self destruct and break down.  Timing belt slippage on a non-interference engine won't cause the engine to self destruct, but it will shut the engine down immediately.  No matter which type of engine you have, if your timing belt breaks on either one of them, you will need to replace it.  Usually, a timing belt will break without any warning at all.