If you need 10% ish accuracy (that could be trimmed and coddled to get to 1-2% ish) then a 555 is fine, especially if you need high voltage capability or high output current capability. Many, many millions are still sold industrially for simple applications such as novelty neon sign power supplies. The 555 itself may change by 1% over the temperature range, a film timing capacitor will be similar, and a timing resistor will add a bit more. There are also effects from noise on the power supply, bypassing of the control voltage and so on. If you make a CMOS 555 oscillator in the kHz range with an NP0 capacitor and a precision timing resistor, it will be pretty good in terms of accuracy and stability with a quiet well-regulated and bypassed power supply. Even if the power supply and external parts are perfect the 555 itself typically drifts 150 ppm/°C, so for a 0-70 °C range that's about a 1% change and the initial accuracy is typically +/-1%. Other oscillator types mentioned below typically operate at much higher frequencies and divide down, so variations in supply, etc. tend to average out, whereas a 10% blip in the supply voltage can truncate a pulse from a 555 a similar amount of time.
If you need a bit better accuracy then a small MPU with built-in calibrated RC oscillator can get 1-2% unadjusted accuracy with no external components. An oscillator based on a ceramic resonators could be sub-1% in initial accuracy. There are also "silicon oscillator" timing chips with a pre-programmed output frequency.
If you need timekeeping accuracy in an oscillator then quartz crystals and oscillators (including those built into MCUs and real-time clock chips) based on them are a good choice. The worst ones tend to be better than 50 ppm (0.005%) and you can get accuracy and stability down into the ppb range with temperature compensated and ovenized oscillators. A watch that loses or gains 2 seconds per day requires an accuracy of about 20 ppm (a 555 oscillator is maybe 1000 times too inaccurate for that application).
Finally, if none of that is good enough, you can even ̶b̶u̶y̶ order atomic clocks as components.
The first two items can be 5-10 cents each in quantity, up to a starting price of about US$5000 for an atomic clock module, so a range of 10,000:1 in cost for an accuracy range of roughly 1,000,000,000:1.