"before the end of the month" incorrectly parsed

Currently a phrase like "before the end of the month" gives an interval as expected, but the end date is not the last day of the month.

Examples:

curl -XPOST http://0.0.0.0:8000/parse --data 'locale=en_US&text=before the end of the month' 
[
    {
        "body": "before the end of the month",
        "dim": "time",
        "end": 27,
        "latent": false,
        "start": 0,
        "value": {
            "to": {
                "grain": "day",
                "value": "2018-11-21T00:00:00.000-08:00"
            },
            "type": "interval",
            "values": [
                {
                    "to": {
                        "grain": "day",
                        "value": "2018-11-21T00:00:00.000-08:00"
                    },
                    "type": "interval"
                }
            ]
        }
    }
]

curl -XPOST http://0.0.0.0:8000/parse --data 'locale=en_US&text=before end of dec'
[
    {
        "body": "before end of dec",
        "dim": "time",
        "end": 17,
        "latent": false,
        "start": 0,
        "value": {
            "to": {
                "grain": "day",
                "value": "2018-12-21T00:00:00.000-08:00"
            },
            "type": "interval",
            "values": [
                {
                    "to": {
                        "grain": "day",
                        "value": "2018-12-21T00:00:00.000-08:00"
                    },
                    "type": "interval"
                },
                {
                    "to": {
                        "grain": "day",
                        "value": "2019-12-21T00:00:00.000-08:00"
                    },
                    "type": "interval"
                },
                {
                    "to": {
                        "grain": "day",
                        "value": "2020-12-21T00:00:00.000-08:00"
                    },
                    "type": "interval"
                }
            ]
        }
    }
]