diff --git a/src/aa_remove_data/remove_data.py b/src/aa_remove_data/remove_data.py
index 4236d58..6db9ae2 100644
--- a/src/aa_remove_data/remove_data.py
+++ b/src/aa_remove_data/remove_data.py
@@ -105,17 +105,17 @@ def get_index_at_timestamp(
         nano (int, optional): Nanoseconds portion of timestamp. Defaults to 0.
 
     Returns:
-        tuple[int, float]: Index of closest sample, difference in seconds
+        tuple[int, float]: Index of closest sample, difference in nanoseconds
         between the target timestamp and sample.
     """
-    target = seconds + nano * 10**-9
-    last_diff = target + 1
+    target = seconds * 10**9 + nano
+    last_diff = target - samples[0].secondsintoyear * 10**9 + samples[0].nano
     for i, sample in enumerate(samples):
-        diff = target - (sample.secondsintoyear + sample.nano * 10**-9)
-        if abs(last_diff) <= abs(diff):
+        diff = target - (sample.secondsintoyear * 10**9 + sample.nano)
+        if abs(last_diff) < abs(diff):
             return i - 1, last_diff
         last_diff = diff
-    return -1, last_diff
+    return len(samples) - 1, last_diff
 
 
 def remove_before_ts(samples: list, seconds: int, nano: int = 0) -> list:
@@ -305,7 +305,6 @@ def aa_remove_data_before():
     parser.add_argument("--new_filename", type=str, default=None)
     parser.add_argument("--backup_filename", type=str, default=None)
     parser.add_argument("--write_txt", action="store_true")
-    parser.add_argument("--block", type=int, default=1)
     args = parser.parse_args()
 
     assert args.filename.endswith(".pb")
@@ -354,7 +353,6 @@ def aa_remove_data_after():
     parser.add_argument("--new_filename", type=str, default=None)
     parser.add_argument("--backup_filename", type=str, default=None)
     parser.add_argument("--write_txt", action="store_true")
-    parser.add_argument("--block", type=int, default=1)
     args = parser.parse_args()
 
     assert args.filename.endswith(".pb")
@@ -375,7 +373,7 @@ def aa_remove_data_after():
     year = pb_header.header.year
     timestamp = args.ts
     assert len(timestamp) <= 6, (
-        "Give timestamp in the form 'month.day.hour.minute.second.nanosecond'. "
+        "Give timestamp in the form 'month day hour minute second nanosecond'. "
         + "Month is required. All must be integers."
     )
     if len(timestamp) == 6: