Rename function `days_1950` to `to_days_1950`

Convert_Matlab/overlap_v6.py

@@ -12,7 +12,7 @@ import sys
 import json
 import datetime
 
-def days_1950(date_num):
+def to_days_1950(date_num):
     """Convert Matlab serial date number to number of days since Jan 1st
     1950.
 
@@ -35,7 +35,7 @@ n_dates = n_eddies.size
 print("n_dates =", n_dates)
 e_overestim = id_child.shape[0]
 print("e_overestim =", e_overestim)
-d_init = days_1950(date_num[0])
+d_init = to_days_1950(date_num[0])
 
 with open("node_id_param.json", "w") as f:
     json.dump({"e_overestim": e_overestim, "d_init": d_init}, f)