Assalamu alaykum, In regards to women traveling. What is the evidence that made the Ulama convert the time (a day and night) into distance (78-80 kilometers) for the purposes of women traveling alone? I have read that some Ulama say it's impermissible regardless of distance without a mahram.

Those who set a distance took the day and night as the distance travelled by camel in that time. Shaykh al-Albani and Shaykh Ibn Uthaymin held that the hadith does not set a distance at all, because its reports differ (a day, a day and night, three days), so whatever people call travel needs a mahram.