Gradually or progressively with the passage of time

धीरे-धीरे समय के साथ

English Usage: The plant grew day by day.

Hindi Usage: पौधा दिन-ब-दिन बढ़ता गया।

As time goes on; with each passing day

जैसे-जैसे समय बीतता है

English Usage: The situation seems to be getting worse by the day.

Hindi Usage: हालात दिन-ब-दिन खराब होते जा रहे हैं।