diff --git a/packages/opencensus-core/src/metrics/export/types.ts b/packages/opencensus-core/src/metrics/export/types.ts
index 877efa459..6597f7bbd 100644
--- a/packages/opencensus-core/src/metrics/export/types.ts
+++ b/packages/opencensus-core/src/metrics/export/types.ts
@@ -121,7 +121,7 @@ export interface TimeSeries {
    * interval (start_timestamp, timestamp]. If not specified, the backend can
    * use the previous recorded value.
    */
-  readonly startTimestamp: Timestamp;
+  readonly startTimestamp: number|null;
   /**
    * The set of label values that uniquely identify this timeseries. Applies to
    * all points. The order of label values must match that of label keys in the
@@ -147,7 +147,7 @@ export interface Point {
    * The moment when this point was recorded. Inclusive.
    * If not specified, the timestamp will be decided by the backend.
    */
-  readonly timestamp: Timestamp;
+  readonly timestamp: number;
   /**
    * The actual point value.
    * 64-bit integer or 64-bit double-precision floating-point number
@@ -253,7 +253,7 @@ export interface Exemplar {
    */
   readonly value: number;
   /** The observation (sampling) time of the above value. */
-  readonly timestamp: Timestamp;
+  readonly timestamp: number;
   /** Contextual information about the example value. */
   readonly attachments: {[key: string]: string};
 }
@@ -309,19 +309,3 @@ export interface ValueAtPercentile {
   /** The value at the given percentile of a distribution. */
   readonly value: number;
 }
-
-export interface Timestamp {
-  /**
-   * Represents seconds of UTC time since Unix epoch
-   * 1970-01-01T00:00:00Z. Must be from 0001-01-01T00:00:00Z to
-   * 9999-12-31T23:59:59Z inclusive.
-   */
-  seconds: number|null;
-  /**
-   * Non-negative fractions of a second at nanosecond resolution. Negative
-   * second values with fractions must still have non-negative nanos values
-   * that count forward in time. Must be from 0 to 999,999,999
-   * inclusive.
-   */
-  nanos: number|null;
-}