The Day Length resource takes a latitude, longitude and Unix timestamp as parameters:
https://api.farmsense.net/v1/daylengths/?d=1350526582&lat=40.360278&lon=-74.957222
and returns a JSON string as follows:
[{
"Error":0,
"ErrorMessage":"",
"TargetDate":"1350526582",
"FormattedDate":"Wed, 17 Oct 2012 22:16:2 -0400",
"Timezone":"",
"Sunrise":"07:14:11",
"Sunset":"18:15:40",
"Daylength":"11:01:29",
"Zenith":"12:44:55",
"Dawn":"06:46:44",
"Dusk":"18:43:07",
"Astrodusk":1350513787,
"Hours_till_dawn":"08:31:25"
}]
You can also specify an array of dates to get day length data over a range of dates: