A soft compass
Your fertile window
The days when conception is most likely — a six-day window ending the day after ovulation.
A note on the math
This uses the standard approximation — ovulation happens about 14 days before your next period. Sperm can live for up to five days inside the body, so the fertile window stretches back five days before ovulation and ends the day after. Trying during this window gives conception its best chance.
Cycles vary, and ovulation day shifts with stress, travel, and life. If you're tracking seriously, basal body temperature, ovulation predictor kits, or cervical-mucus observation can give more personal accuracy than calendar math alone.