1 files changed, 11 insertions, 0 deletions
diff --git a/python/analytics/utils.py b/python/analytics/utils.py
index a67d6f32..ddfc6b23 100644
--- a/python/analytics/utils.py
+++ b/python/analytics/utils.py
@@ -1,7 +1,18 @@
 import numpy as np
 from scipy.special import h_roots
+from dateutil.relativedelta import relativedelta
+import datetime
 
 def GHquad(n : int):
     """Gauss-Hermite quadrature weights"""
     Z, w = h_roots(n)
     return Z*np.sqrt(2), w/np.sqrt(np.pi)
+
+def previous_twentieth(d):
+    r = datetime.date(d.year, d.month, 20)
+    if r > d:
+        r -= relativedelta(months=1)
+    mod = r.month % 3
+    if mod != 0:
+        r -= relativedelta(months = mod)
+    return r