How do I produce a 1Hz clock output using a 555 timer IC? Are there better ways other than a 555 timer IC?
The actual 555 timer frequency depends on the RC time constant, which is strongly affected by variations in the actual resistance and capacitance. The resistor has initial accuracy spec (like 1% or 0.1%) and also varies with temperature. The capacitor also has initial accuracy spec (often +20%/-80% or worse) and varies with applied voltage.

A better way is to use a quartz crystal, such as the commonly available 32.768kHz "tuning fork" watch crystals. Use a series of 15 flip-flops to divide 32.768kHz by \$2^{15}\$ and you get 1Hz, with very high precision.