Delta T
GET /v1/delta-t — Get the Delta T value (UT1 to TT correction) for a given moment.
Delta T
Delta T (ΔT) is the difference between Terrestrial Time (TT) and Universal Time (UT1). It accounts for the irregular rotation of the Earth and is essential for converting between time scales used in astronomical computation.
GET /v1/delta-t
POST /v1/delta-tCredit cost: 1
Parameters
| Parameter | Type | Required | Default | Description |
|---|---|---|---|---|
datetime | string | One of datetime or jd | — | ISO 8601 UTC datetime |
jd | number | One of datetime or jd | — | Julian Day in UT1 |
Response
{
"data": {
"delta_t_seconds": 69.184,
"delta_t_days": 0.000800741,
"jd_tt": 2460388.000801
},
"meta": { "..." }
}| Field | Type | Description |
|---|---|---|
delta_t_seconds | number | ΔT in seconds |
delta_t_days | number | ΔT in Julian Days (seconds / 86400) |
jd_tt | number | The input Julian Day converted to Terrestrial Time |
Examples
curl "https://api.morphemeris.com/v1/delta-t?datetime=2024-03-20T12:00:00Z" \
-H "Authorization: Bearer morphemeris_live_YOUR_KEY"const res = await fetch(
"https://api.morphemeris.com/v1/delta-t?datetime=2024-03-20T12:00:00Z",
{ headers: { Authorization: "Bearer morphemeris_live_YOUR_KEY" } }
);
const data = await res.json();import requests
res = requests.get(
"https://api.morphemeris.com/v1/delta-t",
params={"datetime": "2024-03-20T12:00:00Z"},
headers={"Authorization": "Bearer morphemeris_live_YOUR_KEY"},
)
data = res.json()For current dates, ΔT is approximately 69 seconds. For historical dates, it can vary significantly — over 7,000 seconds for dates around 500 BCE.