This is the motto for my Dad's SWAT team. They wanted to have a Latin translation and which could be put on a shirt, and possibly their new badge.
The phrase "leading the way day and night" is somewhat awkward to translate into Latin, but not completely impossible. The phrase as I understand it is attempting to convey the meaning "placing ourselves before others during both the day and night", an apt ideal for a police force to follow. I will base my initial translations roughly off this, but later provide some which more closely follow your original phrase.
This first one is relatively simple, making use of the present indicative of praepōnō, with both the subject and object being we, and the indirect object (technically object of the preposition prae, which has formed a compound with pōnō) being others. The adjective praevius is also employed to retain some of the original meaning. The preposition in can be omitted rather freely:
Cēterīs [in] diē ac nocte praepōnimus nōs praeviī.
We, leading the way, place ourselves before others [in] day and night.
If you want to emphasize the necessity of the action described, praepōnō in the jussive subjunctive, which expresses a command, might be more suitable:
Praeponāmus cēterīs [in] diē ac nocte nōs praeviī.
Let us, leading the way, place ourselves before others [in] day and night.
If the previous two translations, being more divergent from your original phrase, were not to your liking, the following sentences, which I've written to be much more succinct and less divergent in meaning than the rest, would be equally suitable as well (the second one is, in essence, your original phrase):
Praeviī nōs prae cēterīs diē ac nocte.
[We are] leading the way before others day and night.
Praeviī nōs diē ac nocte.
[We are] leading the way day and night
Since you are using one of these phrases as a motto (which I assume will be printed and displayed somewhere), you might want to consider using a more traditional orthography, which would render the provided phrases as follows:
You can read more about the orthography of Classical Latin here.
Finally, as is with all Latin writing, the word order is mostly free. The provided phrases can technically be rendered in any order, but I would recommend keeping them as such.