1 // Copyright 2020 The Pigweed Authors
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License"); you may not
4 // use this file except in compliance with the License. You may obtain a copy of
5 // the License at
6 //
7 //     https://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
11 // WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
12 // License for the specific language governing permissions and limitations under
13 // the License.
14 #pragma once
15 
16 namespace pw::chrono {
17 
18 enum class Epoch {
19   // The epoch is unkown and possibly even undefined in case the clock is not
20   // always enabled and the epoch may reset over time.
21   kUnknown,
22 
23   kTimeSinceBoot,
24 
25   // Time since 00:00:00 UTC, Thursday, 1 January 1970, including leap seconds.
26   kUtcWallClock,
27 
28   // Time since 00:00:00, 6 January 1980 UTC. Leap seconds are not inserted into
29   // GPS. Thus, every time a leap second is inserted into UTC, UTC falls another
30   // second behind GPS.
31   kGpsWallClock,
32 
33   // Time since 00:00:00, 1 January 1958, and is offset 10 seconds ahead of UTC
34   // at that date (i.e., its epoch, 1958-01-01 00:00:00 TAI, is 1957-12-31
35   // 23:59:50 UTC). Leap seconds are not inserted into TAI. Thus, every time a
36   // leap second is inserted into UTC, UTC falls another second behind TAI.
37   kTaiWallClock,
38 };
39 
40 }  // namespace pw::chrono
41